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mixer: DBM or dual gate mosfet?
hello,
I'm building my first reciver. I can't choose what kind of mixers should I use. I have read that diode ring mixers are far superior compared to dual gate mosfet mixers. Is this true for both - first (RF / VFO) and second (IF / BFO) stages? Or is there any real difference at all? thanks |
mixer: DBM or dual gate mosfet?
On Wed, 01 Mar 2006 01:03:21 -0800, aadu.adok wrote:
hello, I'm building my first reciver. I can't choose what kind of mixers should I use. I have read that diode ring mixers are far superior compared to dual gate mosfet mixers. It depends on what you mean by superior. The mosfet mixer has gain and usually has a lower noise figure. The diode mixer will have superior strong signal handling (higher IP3), but will have about 7dB loss. The diode mixer needs more local oscillator power. They both make excellent mixers if they are applied properly. To get the most bang for your buck, it is hard to beat a ring of 1N914 or 1N4148 diodes at a few cent each. The ferrite 'cups' from scrap Toko IF transformers can be used as cores for the trifilar wound transformers. There are a few other options you should consider. High level IC mixers like the AD831 are worth considering. Switching mixers using MOSFETs are capable of very high performance. Search for info about the N6NWP front-end from QST Feb 93 or the H-mode mixer used in several recent homebrew designs. http://uk.groups.yahoo.com/group/picastar/ http://xoomer.virgilio.it/sergiocartoceti/article_7.htm http://www.warc.org.uk/cdg2000/introduction.htm If you build the receive mixer as a separate module, you can try them all and pick the one that works best for you. 73, Ed. EI9GQ. -- Linux 2.6.15 Remove 'X' to reply by e-mail. Yes, my username really is: nospam |
mixer: DBM or dual gate mosfet?
wrote in message
oups.com... hello, I'm building my first reciver. I can't choose what kind of mixers should I use. I have read that diode ring mixers are far superior compared to dual gate mosfet mixers. "Superior" is something of a loaded word. Whether a particular parts is superior or not depends on your design intent. Probably the most popular mixer for simple HF receivers is the NE/SA 602/612. This is an active mixer. It has amazing amounts of gain, such that an RF stage is almost never needed. It is extremely simple to deploy, and it requires almost no power. Thus, in portable/battery powered circuits it is almost always the mixer of choice. It has an absolutely horrid TOIP. There are other, mostly older, even poorer, active mixers, but the 602 is a very versatile part, so it seems to show up everywhere. At the other extreme are diode ring mixers. These can have stellar TOIPs, but take a lot of oscillator power. Further, they need lots of RF as well, so some sort of RF stage is needed. All this adds up to a need for plenty of power. The best diode ring mixers will use matched, Schottky diodes, but good old 1N4148's do work, and quite well. Many designs use packaged diode ring mixers such as those from Minicircuits. The dual gate MOSFET falls kind of in the middle. It doesn't have the horrible TOIP problems of an active mixer, but it's not as power hungry as a diode ring. The MOSFET seems to have fallen out of favor lately, in spite of being a "balanced" sort of solution. I suspect most designers are either going for power consumption or performance, and really, quite good performance can be had with the active mixers with careful design. Is this true for both - first (RF / VFO) and second (IF / BFO) stages? Or is there any real difference at all? Careful design can manage what the second mixer sees more easily than than the first. This can make the dynamic range problems of an active mixer less of an issue. For that reason, balanced designs that tend toward management of power consumption will sometimes use a diode ring for the first IF and an active mixer for the second. But a superhet bent all out on power conservation will almost always use a pair of 602's. Designers who want to avoid ICs for whatever reason will use a pair of diode rings. I shouldn't sound so down on the 602. A WELL-DESIGNED 602 receiver can easily match the performance of the $1000 class rice box rigs. It cannot, however, come close to the performance of an equally well-designed diode ring rig. But the diode ring rig will probably consume three times the power, meaning three times the heat to deal with and the associated oscillator compensation issues. So you picks your poison. ... |
mixer: DBM or dual gate mosfet?
wrote in message
... If you building a radio that runs on batteries then using more power may be bad. Also keep in mind that more power=more heat If you are building a simple analog VFO, temperature compensating the VFO can be the most tedious part of designing a receiver. Depending on how tight your box is, the difference in heat could be an issue. Keeping the oscillator stable while delivering more power also means more buffer stages between the VFO and the mixer. If you are designing with a DDS, of course, all this is pretty much moot. With a typical DDS chip and a packaged clock oscillator at some high frequency, the oscillator will draw so much current and generate so much heat that what the mixer requires is invisible. ... |
mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
....a long explanation, but a needed one.
One of the most important characteristics of a mixer is its ability to handle large input signals without overloading. if overloaded by an unwanted signal, chances are that it will not be able to handle the weak signal you're interested in. the physical mechanism involved is not important, except for the fact that increasing current through an active mixer (re FET or transistor, or the injection power in a DBM tend to alleviate the problem in some measure. the nois figure of both is more or less equal and adequate in the HF range. the main advantage of the dual gate MOSFET is that it needs much less power from the local oscillator and can save you an amplifying stage. Not really crushing, but sometimes neeedful. If you're talking about a simple first receive I'd go with the MOSFET mixer. there are very good examples in the hand book. iI used them for years with success and still using them in one form or another. the problem is much less severe at the second mixer, because the IF filters tend to defend it from large unwanted signals and the amplituse variations are also smaller due to AGC action. Soooo , KISS (keep it simple, stupid!!!), a very good adage. goood luck with your first. Saandy 4Z5KS |
mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
In article ,
Risto Tiilikainen wrote: If you think the situation in short waves today: Russian and their previous satellite country jammers are quiet Local broadcast is nearly completely in FM Propaganda is no more effective to transmit in short waves Commercial data is practically in Internet. and in satellites Marine communication is in satellites. All this means less cross modulation products in first mixer than some sixteen years ago Atmospheric noise in sw is much higher than the noise of modern front and mixer stage Advantage of diode mixer is marginal There's a good discussion about the advantages and disadvantages of various mixer types, for different applications, in "Experimental Methods in Radio Frequency Design", a book I strongly recommend. As others have pointed out, there's no one right solution. Even for use in what seems like a simple, constant application (e.g. a CW receiver for the 40-meter band), the choice of which is more appropriate can swing one way or the other based on how you intend to use the receiver. As one example given in EMiRFD, if you're looking for a simple receiver which is intended for QRP operation on backpacking trips, then the low power consumption, and the mixer gain of an active mixer such as a Gilbert cell (e.g. SA602 and similar) can make this the ideal. Out in the woods, the RF levels will be low, and the relatively low IP3 of these sorts of mixers isn't likely to be a problem. On the other hand, if you're planning to build a receiver which may have to operate in a strong-adjacent-signal environment (e.g. for Field Day or other contesting), then you may want to favor a diode-ring double-balanced mixer operating at a high LO-injection level, and the devil take the power consumption :-) The FET-switch mixers seem to be a really nice alternative, and although they've gotten relatively little visibility in amateur-radio applications they've become very popular in commercial use (e.g. cell-phone handsets). I haven't yet had a chance to play with these myself but they look like fun! -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
mixer: DBM or dual gate mosfet?
On Wed, 1 Mar 2006 07:03:01 -0500, "xpyttl"
wrote: Probably the most popular mixer for simple HF receivers is the NE/SA 602/612. This is an active mixer. It has amazing amounts of gain, such that an RF stage is almost never needed. It is extremely simple to deploy, and it requires almost no power. Thus, in portable/battery powered circuits it is almost always the mixer of choice. It has an absolutely horrid TOIP. There are other, mostly older, even poorer, active mixers, but the 602 is a very versatile part, so it seems to show up everywhere. If you really intend to use mixers with such horrible IP3 figures, I would suggest using a very selective front end ahead of it. For a single band CW receiver some fixed tuned stages might suffice, but otherwise some tunable input filters should be used. In Europe, there are several high power broadcasters starting at 7100 kHz, which would easily overload the 40 m receiver. Assuming loaded Q of 100 and the front end tuned to 7000 kHz, the -3 dB bandwidth would be +/-35 kHz from the centre frequency with some usable attenuation at 7100 kHz. Using fixed tuned octave wide front end filters with the 602 is just asking for trouble. Paul OH3LWR |
mixer: DBM or dual gate mosfet?
"Paul Keinanen" wrote in message
... In Europe, there are several high power broadcasters starting at 7100 kHz, which would easily overload the 40 m receiver. Assuming loaded Q OH2BT's comments about how much better things have gotten in Europe really made me say hmmmm.... I only recently heard actual measurements, rather than whining, and things are pretty horrible today - they must have been intolerable decades ago. Tight front ends and careful control of levels obviously are important with any mixer, but especially something with the gain of a 602. Nevertheless, I doubt there are many cases where a 602 would be even useable in Europe, let alone "good". ... |
mixer: DBM or dual gate mosfet?
On Thu, 2 Mar 2006 21:11:16 -0500, "xpyttl"
wrote: "Paul Keinanen" wrote in message .. . In Europe, there are several high power broadcasters starting at 7100 kHz, which would easily overload the 40 m receiver. Assuming loaded Q OH2BT's comments about how much better things have gotten in Europe really made me say hmmmm.... I only recently heard actual measurements, rather than whining, and things are pretty horrible today - they must have been intolerable decades ago. We had problems keeping Radio Moscow out of _audio_ equipment :-). Guitar amplifiers were quite problematic with long cables and a top capacitance (the guitar and the player) at the end, bringing quite large RF voltages into the audio stages, causing rectification in unfiltered input stages. Paul OH3LWR |
mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
The FET-switch mixers seem to be a really nice alternative, and although they've gotten relatively little visibility in amateur-radio applications they've become very popular in commercial use (e.g. cell-phone handsets). I haven't yet had a chance to play with these myself but they look like fun! There was an article in the ARRL HB (1995 and probably others) about using an SD5000 quad mosfet as a mixer. I bought a few of these transistors a few years ago (now where did I put them, got lost in the last move!). They are supposed to make a very good mixer. The only disadvantage was the circuit required injection at twice the lo frequency as it used a jk flip flop to develop the required 180 degree injection. I suppose a balum could do the same thing. In any case the AD9954 DDS I am thinking of using can clock to 400mhz and develop output to 160mhz, so getting up to 80mhz (for use with a 9mhz if) would still be no problem. |
mixer: DBM or dual gate mosfet?
On Fri, 03 Mar 2006 22:20:28 -0500, Ken Scharf wrote:
There was an article in the ARRL HB (1995 and probably others) about using an SD5000 quad mosfet as a mixer. Also see N6NWP's article from QST June 1993. And the H-mode mixer by G3SBI in RadCom and various other RSGB publications. I bought a few of these transistors a few years ago... I see the SD5000 is still listed on Calogic's website http://www.calogic.net/html/dmos.html Is the SD5000 still widely available? The search engines turn up a lot of data but very few suppliers. Perhaps a ring of discrete MOSFETs or a fast switch IC like the FST3125 might be a better choice. 73, Ed. EI9GQ. -- Linux 2.6.15 Remove 'X' to reply by e-mail. Yes, my username really is: nospam |
mixer: DBM or dual gate mosfet?
Ken Scharf wrote:
The FET-switch mixers seem to be a really nice alternative, and although they've gotten relatively little visibility in amateur-radio applications they've become very popular in commercial use (e.g. cell-phone handsets). I haven't yet had a chance to play with these myself but they look like fun! There was an article in the ARRL HB (1995 and probably others) about using an SD5000 quad mosfet as a mixer. I bought a few of these transistors a few years ago (now where did I put them, got lost in the last move!). They are supposed to make a very good mixer. The only disadvantage was the circuit required injection at twice the lo frequency as it used a jk flip flop to develop the required 180 degree injection. I suppose a balum could do the same thing. In any case the AD9954 DDS I am thinking of using can clock to 400mhz and develop output to 160mhz, so getting up to 80mhz (for use with a 9mhz if) would still be no problem. Hi ! At the same time Signetics included to the same fet family a double fet SD6000 It was planned for front end applications Single fets were done under type numbers SD305 and SD306 All three were N-channel enhancement types. Positive bias only. I wonder whether Signetics still exists. Signetics was bought by Philips company. I use those fets successfully in one of my conventional type homebrew tranceivers. The first if is having a 10.7 MHz xtal filter. That is mixed down to 455 kHz either with 10.245 MHz or 11.155 MHz xtal Sideband selection is done with the selection of mixing direction. 455 kHz is using Collins mechanical filter having very good shape factor and special skirt for lower sideband use. 73, Risto OH2BT |
mixer: DBM or dual gate mosfet?
I see the SD5000 is still listed on Calogic's website http://www.calogic.net/html/dmos.html Is the SD5000 still widely available? The search engines turn up a lot of data but very few suppliers. Perhaps a ring of discrete MOSFETs or a fast switch IC like the FST3125 might be a better choice. 73, Ed. EI9GQ. GM Ed. Certainly a better choice when it comes to conversion loss. I've built a half dozen SD5000 mixers and although at least one of them managed a measured +50 dBm Ip3, (G3SBI measured it not me!) I never managed to get the conversion loss below 9 dB and more often 10. Conversely, the 3125/ family readily does 4.8 dB conversion loss thanks to the very respectable Rds on. REALLY simplifies things in the front end department, to at least 30 MHz, with attention paid to the front end filters, you can get away without an RF amplifier. Regards W4ZCB |
mixer: DBM or dual gate mosfet?
GM Ed. Certainly a better choice when it comes to conversion loss. I've built a half dozen SD5000 mixers and although at least one of them managed a measured +50 dBm Ip3, (G3SBI measured it not me!) I never managed to get the conversion loss below 9 dB and more often 10. Conversely, the 3125/ family readily does 4.8 dB conversion loss thanks to the very respectable Rds on. REALLY simplifies things in the front end department, to at least 30 MHz, with attention paid to the front end filters, you can get away without an RF amplifier. Regards W4ZCB Hi all, Harold, W4ZCB, has given some "comments" on the H-Mode Mixer that are REAL and TRUE. G3SBI has removed the mixer from the stages that are critical on a receiver and in the CDG2000 project it was demonstrated the IMD due to passive components like core of coils. The FST3125 fast bus switch has lowered the conversion loss of the H-Mode Mixer and made the RX front end "hot", although not reaching the IP3 of +50dBm it still has plenty of +dBm to give ...around +40dBm!You can permit yourself to add a xtal filter behind the h-mode mixer and still getting high numbers on IP3. If you are looking for a low consumption and simple mixer you may go OK with the classic NE/SA602 and similar ones. BUT ... if you are looking for high performance you need the H-Mode Mixer in the 3 transformer G3SBI or the 2 transformer I7SWX configurations. The H-Mode Mixer has been tested on downconversion (CDG2000, STAR projects) and also on upconversion projects (I7SWX). For upconversion I have devised a new squarer using LVDS and test it at IF of 35 to 70 MHz (and 100MHz) with conversion loss around -5dbm and IP3 between +35 to +40dBm (3.3V FST3125). The H-Mode Mixer has been tested for RF input up to 50MHz in RX and converter to 27-28MHz IF. At 144MHz it performs like a standard diode db mixer having a conv loss around -8dB. The input limit is due to the internal gates timing and unbalancing as the FST3125 may have a bandwidth between 300 to 400MHz. For those interested I may suggest a visit to JA9TTT web page where he has reported measurement on both G3SBI and I7SWX versions using the 74AC86 squarer with balance adjustment. The comments are in japanese but a translator is making the reading understandable : ja9ttt.homedns.org/. I have posted a copy in my web page www.qsl.net/i7swx in the subdirectory homebrewing. JA9TTT page permits to enlarge the spectrum analyzer screen pictures. I have also developed a 1 transformer double balance mixer/demodulator/modulator using the FST3125 and 74AC/HC86 squarer with an IP3 of around +25dBm. Notes on the H-Mode Mixers and 1T DBM have been reported in RadCom, G3VA's Technical Topics column. For those interested on more detailed information I can make available notes in English and Italian. Please write to my e-mail address:. 73 Gian I7SWX F5VGU W1-I7SWX G-QRP #10241 I QRP #571 |
mixer: DBM or dual gate mosfet?
What is the IP3 of a typical dual gate MOSFET mixer?
One can also use HC4066 or 4053 as the switching element at lower freqs. JJ |
mixer: DBM or dual gate mosfet?
What is the IP3 of a typical dual gate MOSFET mixer?
One can also use HC4066 or 4053 as the switching element at lower freqs. JJ I really do not know what is the IP3 of a DG Mosfet as I never have seen any value reported. I hope some readers may have data on this. Certainly we have to look at IIP3 and OIP3 as the DGM mixer may have high conversion gain 15-20dB and is somewhat limited in dynamic range. Maybe it could have an OIP3 around +5dBm equivalent to an IIP3 of -10 to -20dBm .... more or less similar to the NE602. The DGM mixer was a common mixer in the first series of transistorized RTX with valves PA (FT101Z, TS820 etc). The DGM has a good square law, better than JFET. 74HC4066 is OK at low frequency conversion but it has a haigh conversion loss, around 8-10dB and so associated noise figure. Today the switched mixer should use fast bus switches like the FST3125 family when looking at high performance mixers. The examples are the CDG 2000 and STAR (Pic-A-Star) projects with IP3 around +40dBm and +36dBm, where the H-Mode Mixer with FST3125 is used. 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
Anyone remember the CA3028 singly balanced mixer?
It was just 2 transistors as difference amp and current source transistor. What would the IP3 be for it? JJ |
mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
Why use a AD831 if the noise figure is 10dB? It has gain, high IP3 and 10db my mixer standard is not that bad. A low gain RFamp with low noise figure will override mixer noise. Of course the RFamp must have a good IP3 as well. Allison Ok, I like to try the AD831. When is dual supply better than single ended? There must be a socket to fit the package but is it all right to solder tiny leads to it for prototyping? JJ |
mixer: DBM or dual gate mosfet?
Hi all,
Allison has given important information on mixers data. His comments are very usefull. I would like to underscore the last note: All of that is good but unless the post mixer amp, IF and filters following it are up to the task and well matched the results can be very disappointing. When going to that level of performance one needs to look at the recieving system and examine carefully. It is right to relook at a receiver design when selecting a high performance mixer. The limiting problems will show up in other stages as the improuvements may not be very detectable.... amplifiers, filters, l.o. phase noise... Well one need to start from somewhere to improuve a receiver. If the non mixer stages have a maximum IP3 of around +15dBm, certainly a +35/40dBm mixer may not make much of a difference, unless it is replacing a NE602. In this case you may use the I7SWX 1 transformer double balanced mixer using the FST3125 (half of an H-Mode mixer) with an IP3 of +25dBm. As an example, I defined with afriend of mine a mod on the Elekraft K2. The 1st mixer (TUF) was replaced by an I7SWX 2T H-Mode Mixer followed by a 10kHz BW 2 xtal roofing filter . Two tones at 7.050 and 7.070 MHz IP3 Results of the K2 we Original mixer: +15dBm with H-Mode Mixer: +27dBm as you may see these are important differences. The actual limiting stage is the original post mixer amplifier. 73 Gian I7SWx |
mixer: DBM or dual gate mosfet?
"Giancarlo Gian Moda, I7SWX" wrote in
ups.com: Well one need to start from somewhere to improuve a receiver. If the non mixer stages have a maximum IP3 of around +15dBm, certainly a +35/40dBm mixer may not make much of a difference, unless it is replacing a NE602. In this case you may use the I7SWX 1 transformer double balanced mixer using the FST3125 (half of an H-Mode mixer) with an IP3 of +25dBm. Gian I7SWx That is a very interesting suggestion. Where can I find the 1 transformer DBM using the FST3125? JJ |
mixer: DBM or dual gate mosfet?
Hi JJ,
the note on the 1T DBM was reported in RadCom, Technical Topics column, June 2004. I asked a friend to insert all mixer infos in my web page www.qsl.net/i7swx but I do not know when he will be able to do it. In my web page in homebrewing you my read the experiences and measuremnts done by JA9TTT on both versions (3T & 2T) of the H-Mode Mixer. This is a software package translation from japanese but it is understandable. You will be able to see Spectrum Analyzer measurents too. If you send me (callsignatyahoo.com) your e-mail address I can send you the complete 1T DBM note in english (more stuff than in TT). A NOTE for ALLISON ... I see you have been fiddling with DEC stuff. Were you working for DEC or a customer? I was with DEC for a quarter of a century ...hi 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
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mixer: DBM or dual gate mosfet?
Hi Allison, From '83 to '93. Had a 6digit number as I was part of CSSE and central engineering for high end printing systems. I really liked the Mill. Ah..OK CSSE ... I sold a PDP11/10 with a card reader from CSS to the Italian Goverment as a donation to a University in Peru'...the highest PDP11 installation on the world at that time...hi Ah, the plastics fire if memory serves. Never played with any of the 15bit hardware or the controls. Just PDP-8, 10, 11 and VAX. OK. PDP9 and 15 wer 18bits .. I did some work on DEC10, 11 and when the VAX came out I was in sales... I made some of the first sales in Italy and most of my VAXes were linked in Decnet to PDP11/70 and 45. Just finishing up a 85W brick for it now. Nice power. On 6 meters I have an FT726 with the 50MHz converter (RX) supermodified ... the only original pieces are 1x Jfet and 2 IFTs ...hi. I also have an FT920 a Xmas gift (a few years ago) from my good FRIEND (with capital letters !!!) Art (and his wife)...hi Just talked to him this weekend! He's about 30miles NE of me. Next net I'll mention you name and say HI.. One of his project was to restart the old AM nets, he's got maybe 6-8 regulars. How nice... Too bad we did not get in touch during my business quarterly trips in W1 (for confessions with my boss 2000 to 2003...hi). I was usually at K1GBX house at weekends ... eating lobsters and other good stuff...hi.When I took my wife and my daugther Luisa for her first trip we even had a story in a local newspaper and picture...hi I m sure when you will tell him we had this kbd chatting he will jump on his chair and get crazy...hi For a jike tell him we had a QSO on 6 meter SSB... than you will tell him the true story...hi Small world, smaller if we get some propagation. Yes, amateur radio makes the world really small, some time ... hi Sorry for this non Mixers conversation for our friends.... I will comment on the following... 73 Gian I7SWX Allison KB1GMX , |
mixer: DBM or dual gate mosfet?
The 602 is now replaced with the 612 but is still an old design.
If you design your mixer ( /doubler ) with AD8343 and use proper RF transformers from CoilCraft, it just cannot go wrong... ( well, Murphy et al of course... ) Da / M0DFI Hi Dan, Yes the AD8343 is an interesting mixer... but for me it may be too noisy (10dB). THe IP3 is certainly much better (+15dBm) than the 602/612 (-15dBm), but this one has a lower NF of 5dB. If you build my 1 homebrew transformer (50c) FST2125 DBM you do get am IP3 of +25dBm NF 5dB ... adding a post mixer 10dB LNA you probably get a 3dB NF. Certainly you have to select the most valid mixer for the specific project as always we have to compromise and give priority to one of the many parameters. 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
go with the simplest one! something like a dual gate FET: that's going
to ease problems with the local oscillator. But build it as a separate module on a small PCB, and wire it in. that way you'll be able to experimwnt later on by replacing the module. that way you can go from easy and simple to complex and high perfoemance. for a first it hard to beat the method. i see you're getting too much info, especially for a newcomer! stay in touch, I'll try to help you to the limit of my abilities. Saaandy 4Z5KS |
mixer: DBM or dual gate mosfet?
guys, bear in mind that the intercept point is primarily a function of
the operating quiescent poit. you cam make it high, really high and get superlative mixers, even single ended. i designed one aroun the now defunct VMP4 from Siliconix with an Id of 500mA!!! the damned thing had nearly +50dB IP#. About the same went with the LNA. All in all 24W power dissipated in the front end. How many of us can afford that or need that for the matter? drop it! what the guy needs is some reasonable value of dynamic range and around 10-12 dB for IP3. he isn't going to build a radio telescope receiver on his first attempt. Be reasonable! with FET's the thing to ensure is that the operating point is setablished with Vgs set at about half of the pinchoff voltage to ensure maximum dynamic range. a noise figure under 10dB is adequate for HF. it's not the galactic noise that limits your reception! Saandy 4Z5KS |
mixer: DBM or dual gate mosfet?
Hi Saandy,
I have some russian power FET similar to the VMP4 and probably better but there is no sense to use them as they are no more in production and diffcult to purchase in East Europe. I believe a discussion on Mixers is important particularly for a newcomer. He must know all the different kind of mixers than he will have to decide.... it is like talking about small car or motobykes because it is better run with a bicycle...one should not know about racing car or motobykes.... he can putchase a byke tha add a little mosquito engine or pss to a bigger motobyke or a small car later ... but he will know what he has (he will have to push a lot with his legs and then see to push less or not at all).... it is like for a portable RTX were consumption is at premium... you cannot put (probably an h-mode mixer has you will have to spend 30-50mA plus an amplifier with other 20mA versus a NE612 that needs 3mA !!! To hell the IP3... one can use his brain as a DSP...hi 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
On 28 Mar 2006 12:36:21 -0800, "Giancarlo Gian Moda, I7SWX"
wrote: Ah..OK CSSE ... I sold a PDP11/10 with a card reader from CSS to the Italian Goverment as a donation to a University in Peru'...the highest PDP11 installation on the world at that time...hi By the way, did you have to install extra fans to compensate for the low air density (and thus lower heat carrying capacity) at high altitudes ? Some electronic systems have quite low maximum altitude ratings due to this. The low air density might also cause problems for amateur radio equipment if operated at full power at high altitudes. Paul OH3LWR |
mixer: DBM or dual gate mosfet?
Hi Paul,
This installation was somewhere on the Andes were there was a astronomic site. We did not need to use extra fans or other "helping" devices. Certainly this set-up was not on an open air site, it was in an building. So "air" presence was OK for humans. BTW, in 1966 while working in UK for a small specialized company, I was involved in a project were we were producing the Eidofor Colour TV Projectors (Philips Group). Philips had sold 3 of these units to be used in Mexico City for the Olympic Games. To be sure we would not have problems with the 3 colour tubes for explosion (I forgot M.C. height a.s.l.) we tested the system in the BAC UK air chamber (vy expensive tubes...hi). 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
Hi Allison,
OK for everything. Please keep me updated on Art's reaction...hi 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
On 1 Apr 2006 00:40:31 -0800, "Giancarlo Gian Moda, I7SWX"
wrote: Hi Paul, This installation was somewhere on the Andes were there was a astronomic site. Apparently this was much before the Atacama site in Chile became popular. We did not need to use extra fans or other "helping" devices. Certainly this set-up was not on an open air site, it was in an building. So "air" presence was OK for humans. At sea level, the air density is about 1.2 kg/m³ and at altitudes of 4000 m (La Paz?), the air density is only 0,8 kg/m³. In a forced cooled system, the critical parameter is the _mass_ flowing though the system and the amount of degrees the air is heated. In order to run the same mass of air through the system, you would have to use 1.2:0.8 or 1.5 times the air volume in the mountains. BTW, in 1966 while working in UK for a small specialized company, I was involved in a project were we were producing the Eidofor Colour TV Projectors (Philips Group). Philips had sold 3 of these units to be used in Mexico City for the Olympic Games. To be sure we would not have problems with the 3 colour tubes for explosion (I forgot M.C. height a.s.l.) we tested the system in the BAC UK air chamber (vy expensive tubes...hi). Wasn't Eidophores used during the Apollo flights to show the orbits in Huston ? Paul OH3LWR |
mixer: DBM or dual gate mosfet?
Wasn't Eidophores used during the Apollo flights to show the orbits in
Huston ? Paul OH3LWR Hi Paul, I do not know but in middle of 60s that was the only TV color projectors designed by a Swiss engineer, assembled by Peto Scott Instrument Ltd for Philips in Addlestone, Surrey UK. It was tested in the central lab were we were mainly working on military equipments. Many of those big blocks were sold world wide. I do remember the Mexico Olympics because we had to do that special test in the chamber room were airplanes were tested for all 3 machines. For Peru', I believe it was somewhere over 2000 meters asl and it was not later than 1980. 73 Gian I7SWX |
mixer: DBM or dual gate mosfet?
Wasn't Eidophores used during the Apollo flights to show the orbits in
Huston ? Paul OH3LWR Hi Paul, I do not know but in middle of 60s that was the only TV color projectors designed by a Swiss engineer, assembled by Peto Scott Instrument Ltd for Philips in Addlestone, Surrey UK. It was tested in the central lab were we were mainly working on military equipments. Many of those big blocks were sold world wide. I do remember the Mexico Olympics because we had to do that special test in the chamber room were airplanes were tested for all 3 machines. For Peru', I believe it was somewhere over 2000 meters asl and it was not later than 1980. 73 Gian I7SWX |
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