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Homebrew projects
I really enjoyed the message thread sparked by the pictures of
Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: 40 meter DSB phone HB: UK hams recently got a doubling of their 40 meter freq allocation and can now go up to 7.2 Mhz. I built a simple 40 meter DSB transmitter. Solid state. VFO. Built it on a wooden cutting board (almost a real breadboard. Puts out about 2 watts. I run it into a heavily modified Ramsey kit linear. Then to a HB balanced tuner, TV lead up to the inverted U dipole. Works fine. Lots of fun. I use it with my Drake 2B, but plan on pressing into service my HB "Mate for the Mighty Midget" RX (see web site) (I have a 455 kc filter that I'll install eventually -- right now it is very broad). 17 SSB phone: I have a HB 17 meter SSB TX (see my web site). I' also use it with the 2B, but changing bands is a pain. So I'm building a dedicated RX for 17. I have a Doug DeMaw "Barbados" reciever (someone else put the components on a "Circuit Boards Specialists" board. It has a 5Mhz ladder filter that I've broadened for pnone. I tried running the VFO at around 13 Mhz with varactor tuning, but it was unstable, so I'm going VXO. With 2 rocks in the 23 Mhz range I shoud cover the phone portion of 17. More later... Any comments or suggestions? How about following Dale's lead and posting updates on projects? 73 Bill N2CQR M0HBR CU2JL http://planeta.clix.pt/n2cqr |
The group may find the picture and very brief discussion of my homebrew gear
on QRZ.COM interesting. Bill W0IYH "Bill N2CQR MOHBR" wrote in message om... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... |
"Bill N2CQR MOHBR" wrote in message om... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: Hi Bill, I have trouble keeping up with where in the world you are, but visit your site regularly to see what you are up to. I would encourage others to brew their own xtal filters. uP xtals are cheap enough today that you can buy a pile and match up what you need. W7ZOI's articles on crystal filters takes the mystery out. Probably the most difficult part is characterizing individual crystals so you can plug in the numbers. I use an HP network analyzer, but Wes also shows a test jig for doing this. Alternatively, N2PK's VNA will do an excellent job. In the end, you can make better filters than you can buy- and for a heck of a lot less $$. N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz filter; the other with a homebrew 250 Hz filter- it took no imagination to discern which one was cleaner. Now, I'll go have a look at Bill W0IYH's site. Dale W4OP |
Bill: Very FB! I especially liked the Velvet Vernier in there amidst the
digitial readouts. In my 17 meter SSB TX I used an old Simpson meter that I had found in a radio club junk box back in 1974. Thanks for sharing those inspirational pictures. 73 Bill N2CQR M0HBR CU2JL http://planeta.clix.pt/n2cqr "William E. Sabin" wrote in message news:2HS1e.1208$Vx1.663@attbi_s01... The group may find the picture and very brief discussion of my homebrew gear on QRZ.COM interesting. Bill W0IYH "Bill N2CQR MOHBR" wrote in message om... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... |
Dale: I was faced with doing the complex analysis of the individual
crystal parameters when I was building my first superhet (W1FB's "Barebones" aka "Barbados" RX). I just skipped all of the analysis and used the same capacitor values that Doug had used in his version. I'm sure my filter's passband wasn't nearly as pretty as it could have been, but it definitely produced the desired "single signal effect." I was happy. As I mentioned in the earlier post, I have an 80/40 meter tube type RX (Mate for the Mighty Midget"). It has a 455 kHz IF. This makes homebrew filter making difficult! I tried, but crystals were hard to come by in that freq range. In the end, I threw in the towel and just used a 455 Khz IF can in lieu of the filter. Great for listening to AM! But now I want to narrow it down a bit, so I'm thinking about yanking out the IF can and replacing it with a commercial 455 kc filter from the junkbox. I need to figure out how to handle the impedance matching issues (input and output). 73 Bill M0HBR N2CQR CU2JL http://planeta.clix.pt/n2cqr "Dale Parfitt" wrote in message news:Qx_1e.34384$oa6.2111@trnddc07... "Bill N2CQR MOHBR" wrote in message om... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: Hi Bill, I have trouble keeping up with where in the world you are, but visit your site regularly to see what you are up to. I would encourage others to brew their own xtal filters. uP xtals are cheap enough today that you can buy a pile and match up what you need. W7ZOI's articles on crystal filters takes the mystery out. Probably the most difficult part is characterizing individual crystals so you can plug in the numbers. I use an HP network analyzer, but Wes also shows a test jig for doing this. Alternatively, N2PK's VNA will do an excellent job. In the end, you can make better filters than you can buy- and for a heck of a lot less $$. N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz filter; the other with a homebrew 250 Hz filter- it took no imagination to discern which one was cleaner. Now, I'll go have a look at Bill W0IYH's site. Dale W4OP |
Thanks Bill. The Velvet Vernier dial is not only a very good and beautiful
dial, it is excellent nostalgia for an era that has just about disappeared. Bill W0IYH "Bill N2CQR MOHBR" wrote in message om... Bill: Very FB! I especially liked the Velvet Vernier in there amidst the digitial readouts. In my 17 meter SSB TX I used an old Simpson meter that I had found in a radio club junk box back in 1974. Thanks for sharing those inspirational pictures. 73 Bill N2CQR M0HBR CU2JL http://planeta.clix.pt/n2cqr "William E. Sabin" wrote in message news:2HS1e.1208$Vx1.663@attbi_s01... The group may find the picture and very brief discussion of my homebrew gear on QRZ.COM interesting. Bill W0IYH |
"Bill N2CQR MOHBR" wrote in message om... Dale: I was faced with doing the complex analysis of the individual crystal parameters when I was building my first superhet (W1FB's "Barebones" aka "Barbados" RX). I just skipped all of the analysis and used the same capacitor values that Doug had used in his version. I'm sure my filter's passband wasn't nearly as pretty as it could have been, but it definitely produced the desired "single signal effect." I was happy. As I mentioned in the earlier post, I have an 80/40 meter tube type RX (Mate for the Mighty Midget"). It has a 455 kHz IF. This makes homebrew filter making difficult! I tried, but crystals were hard to come by in that freq range. In the end, I threw in the towel and just used a 455 Khz IF can in lieu of the filter. Great for listening to AM! But now I want to narrow it down a bit, so I'm thinking about yanking out the IF can and replacing it with a commercial 455 kc filter from the junkbox. I need to figure out how to handle the impedance matching issues (input and output). 73 Bill M0HBR N2CQR CU2JL Hi Bill, I too built the Barbados RX- don't know what happened to it though. Have you thought of using a Murata ceramic filter in your tube RX? They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will be an improvment over what you have. Typcial Zin and Zout is around 1K. Although I have never tried it, I wonder about the possibility of brewing your own ceramic filter from some of Murata's 455KHz ceramic resonators. Although not the Q of a quartz crystal, it may be worthwhile. I have some here and think I'll put one on the network analyzer and see what characteristics I get. Dale W4OP |
Dale: Wow, another Barbados RX builder. That was my first successful
superhet project. I now have the one I built (still on 20), and this morning I got another one (the one built by someone else on a factory-made board)going on 17 with a VXO. I have a THIRD partially built Barbados RX board. If this keeps up, I'll soon have a BBRX museum. As for the tube RX, I have a Toyo Communications CM filter. Markings look good: "445 -- 2.4 -- C" Now I have to figure out how to work this into the existing RX circuitry. Time to look through some mid-'60s handbooks and QSTs. 73 Bill M0HBR CU2JL N2CQR http://planeta.clix.pt/n2cqr Hi Bill, I too built the Barbados RX- don't know what happened to it though. Have you thought of using a Murata ceramic filter in your tube RX? They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will be an improvment over what you have. Typcial Zin and Zout is around 1K. Although I have never tried it, I wonder about the possibility of brewing your own ceramic filter from some of Murata's 455KHz ceramic resonators. Although not the Q of a quartz crystal, it may be worthwhile. I have some here and think I'll put one on the network analyzer and see what characteristics I get. Dale W4OP |
The Murata filters range between 1.5k and 2k.
Pete "Bill N2CQR MOHBR" wrote in message om... Dale: Wow, another Barbados RX builder. That was my first successful superhet project. I now have the one I built (still on 20), and this morning I got another one (the one built by someone else on a factory-made board)going on 17 with a VXO. I have a THIRD partially built Barbados RX board. If this keeps up, I'll soon have a BBRX museum. As for the tube RX, I have a Toyo Communications CM filter. Markings look good: "445 -- 2.4 -- C" Now I have to figure out how to work this into the existing RX circuitry. Time to look through some mid-'60s handbooks and QSTs. 73 Bill M0HBR CU2JL N2CQR http://planeta.clix.pt/n2cqr Hi Bill, I too built the Barbados RX- don't know what happened to it though. Have you thought of using a Murata ceramic filter in your tube RX? They make a 4KHz unit for under $3. Not CW selectivity, but I'll bet it will be an improvment over what you have. Typcial Zin and Zout is around 1K. Although I have never tried it, I wonder about the possibility of brewing your own ceramic filter from some of Murata's 455KHz ceramic resonators. Although not the Q of a quartz crystal, it may be worthwhile. I have some here and think I'll put one on the network analyzer and see what characteristics I get. Dale W4OP |
Dale - regarding homebrew crystal filters - I wonder if you or any others here have looked at Elecraft's crystal filter implementation in the K2? It's built with discrete crystals and the bandwidth is variable over a large range. Haven't seen that design exploited elsewhere, but don't know why. It sure works well. K8AC |
"Bill N2CQR MOHBR" wrote in message om... Dale: Wow, another Barbados RX builder. That was my first successful superhet project. I now have the one I built (still on 20), and this morning I got another one (the one built by someone else on a factory-made board)going on 17 with a VXO. I have a THIRD partially built Barbados RX board. If this keeps up, I'll soon have a BBRX museum. Hi Bill, Did I sell you mine years ago? I seem to recall using a temp stabilized varicap in a shielded enclosure for main tuning. It was done on a factory board. Or was that a 6M xverter I sold? Dale |
Although I have never tried it, I wonder about the possibility of brewing your own ceramic filter from some of Murata's 455KHz ceramic resonators. Although not the Q of a quartz crystal, it may be worthwhile. I have some I've done this with ceramic filters in tube circuits. You definatly need to match the impedence to the tubes wich is high both for plate and grid. What I did for that was to use a transistor IF can, filter, IF can wired so the high impedence side was to the grids and plates. Worked very well in a tube RX like the mighty midget. For transistors the matching for those filters is IF can to get the high collector impedence down to 1k range then the filter into the base of the transistor. FETs get treated like tubes. Allison KB1GMX |
Dale: Wow, small world! Yea I think that is the one I'm working on. I think
you also had a DC-DC converter to bring the voltage to the varicaps up. Very nice enclosure for the oscillator. I now have it percolating nicely as a VXO around 23 Mhz (for the 17 meter band). Bill "Dale Parfitt" wrote in message news:0ez2e.30158$191.23924@trnddc02... "Bill N2CQR MOHBR" wrote in message om... Dale: Wow, another Barbados RX builder. That was my first successful superhet project. I now have the one I built (still on 20), and this morning I got another one (the one built by someone else on a factory-made board)going on 17 with a VXO. I have a THIRD partially built Barbados RX board. If this keeps up, I'll soon have a BBRX museum. Hi Bill, Did I sell you mine years ago? I seem to recall using a temp stabilized varicap in a shielded enclosure for main tuning. It was done on a factory board. Or was that a 6M xverter I sold? Dale |
"Bill N2CQR MOHBR" wrote in message om... Dale: Wow, small world! Yea I think that is the one I'm working on. I think you also had a DC-DC converter to bring the voltage to the varicaps up. Very nice enclosure for the oscillator. I now have it percolating nicely as a VXO around 23 Mhz (for the 17 meter band). Bill That's it Bill! Amazing. Hopefully I placed the Dc-DC converter inside that shielded enclosure. Glad it has a good home. I believe that board was from A&A Engineering- seem to recall they supplied for QST back then. That design was a very robust RX. Doug (?) had sent me the companion TX article before release- but I never got around to building it. How many countries has that RX travelled to now? Dale W4OP Dale |
"Floyd Sense" wrote in message ... Dale - regarding homebrew crystal filters - I wonder if you or any others here have looked at Elecraft's crystal filter implementation in the K2? It's built with discrete crystals and the bandwidth is variable over a large range. Haven't seen that design exploited elsewhere, but don't know why. It sure works well. K8AC That filter topology was, I think, first used by Ten Tec in their Scout. From a purist standpoint there can be problems: 1. Asymmetrical skirts 2. Changing IN/OUT Z with BW 3. Shifting center freq as the BW is narrowed ( capacity loading) 4. I am guessing here, but I would think the group delay would suffer at one end or the other 5. Passband ripple can become excessive as BW is increased. I looked at this approach, along with a method described in QEX last year for dealing with the center freq shift, but came to the conclusion that I could design a much better filter if I optimized each BW- even though it took 3 filters. One aspect of filters that has long been either ignored or overlooked ( even though W7ZOI details it in EMRFD) is group delay. A friend (N2PK) recently sent me 2 WAV files of a Yaesu 1000 stock 250Hz filter and his homebrew 250 Hz filter. The difference was remarkable- his filter was much cleaner and crisper sounding, no ringing. Great care was taken with group delay in his design. Dale W4OP |
It would be interesting to know what was different about his filter. Do you
know? K8AC "Dale Parfitt" wrote in message news:3Q03e.27300 snip One aspect of filters that has long been either ignored or overlooked ( even though W7ZOI details it in EMRFD) is group delay. A friend (N2PK) recently sent me 2 WAV files of a Yaesu 1000 stock 250Hz filter and his homebrew 250 Hz filter. The difference was remarkable- his filter was much cleaner and crisper sounding, no ringing. Great care was taken with group delay in his design. Dale W4OP |
Dale Parfitt wrote:
"Bill N2CQR MOHBR" wrote in message om... Dale: Wow, small world! Yea I think that is the one I'm working on. I think you also had a DC-DC converter to bring the voltage to the varicaps up. Very nice enclosure for the oscillator. I now have it percolating nicely as a VXO around 23 Mhz (for the 17 meter band). Bill That's it Bill! Amazing. Hopefully I placed the Dc-DC converter inside that shielded enclosure. Glad it has a good home. I believe that board was from A&A Engineering- seem to recall they supplied for QST back then. That design was a very robust RX. Doug (?) had sent me the companion TX article before release- but I never got around to building it. How many countries has that RX travelled to now? Dale W4OP Dale Dale: I can't remember when it was that I bought it from you. So, depending on the date, it could have spent time in the Dominican Republic, Northern Virginia, the Azores Islands of Portugal, and the UK. BTW, I always admired the neat construction of that RX. The hookup wire used was very nice. Do you remember what kind of wire you were using. I'd like to get some of that. Makes a big difference in the appearance of the final product. 73 Bill N2CQR CU2JL M0HBR http://planeta.clix.pt/n2cqr |
On Mon, 28 Mar 2005 21:19:44 GMT, "Dale Parfitt"
wrote: "Bill N2CQR MOHBR" wrote in message . com... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: Hi Bill, I have trouble keeping up with where in the world you are, but visit your site regularly to see what you are up to. I would encourage others to brew their own xtal filters. uP xtals are cheap enough today that you can buy a pile and match up what you need. W7ZOI's articles on crystal filters takes the mystery out. Probably the most difficult part is characterizing individual crystals so you can plug in the numbers. I use an HP network analyzer, but Wes also shows a test jig for doing this. Alternatively, N2PK's VNA will do an excellent job. In the end, you can make better filters than you can buy- and for a heck of a lot less $$. N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz filter; the other with a homebrew 250 Hz filter- it took no imagination to discern which one was cleaner. Now, I'll go have a look at Bill W0IYH's site. Dale W4OP Dale & Bill, Jim, K8IQY has the Precision VXO and Crystal test rig that uses the PVXO as a driver for the candidate IF filter crystal under test. I'm currently building both of those. 73, Ted KX4OM |
On Mon, 28 Mar 2005 21:19:44 GMT, "Dale Parfitt"
wrote: "Bill N2CQR MOHBR" wrote in message . com... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: Hi Bill, I have trouble keeping up with where in the world you are, but visit your site regularly to see what you are up to. I would encourage others to brew their own xtal filters. uP xtals are cheap enough today that you can buy a pile and match up what you need. W7ZOI's articles on crystal filters takes the mystery out. Probably the most difficult part is characterizing individual crystals so you can plug in the numbers. I use an HP network analyzer, but Wes also shows a test jig for doing this. Alternatively, N2PK's VNA will do an excellent job. In the end, you can make better filters than you can buy- and for a heck of a lot less $$. N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz filter; the other with a homebrew 250 Hz filter- it took no imagination to discern which one was cleaner. Now, I'll go have a look at Bill W0IYH's site. Dale W4OP Dale, I checked in late on this thread; what is Bill Sabin's site URL? I've been Googleing to beat the band, but it doesn't turn up. Ted KX4OM |
"Ted Bruce" wrote in message
... On Mon, 28 Mar 2005 21:19:44 GMT, "Dale Parfitt" wrote: "Bill N2CQR MOHBR" wrote in message .com... I really enjoyed the message thread sparked by the pictures of Dale's very FB HB RX. We need more of that kind of discussion... Here is what I've been working on in London: Hi Bill, I have trouble keeping up with where in the world you are, but visit your site regularly to see what you are up to. I would encourage others to brew their own xtal filters. uP xtals are cheap enough today that you can buy a pile and match up what you need. W7ZOI's articles on crystal filters takes the mystery out. Probably the most difficult part is characterizing individual crystals so you can plug in the numbers. I use an HP network analyzer, but Wes also shows a test jig for doing this. Alternatively, N2PK's VNA will do an excellent job. In the end, you can make better filters than you can buy- and for a heck of a lot less $$. N2PK recently sent me 2 WAV files- one recorded with the 1000MP stock 250 Hz filter; the other with a homebrew 250 Hz filter- it took no imagination to discern which one was cleaner. Now, I'll go have a look at Bill W0IYH's site. Dale W4OP Dale & Bill, Jim, K8IQY has the Precision VXO and Crystal test rig that uses the PVXO as a driver for the candidate IF filter crystal under test. I'm currently building both of those. Ted KX4OM K8IQY web page for this test rig http://www.k8iqy.com/testequipment/pvxo/pvxopage.htm w9gb |
Dale, I checked in late on this thread; what is Bill Sabin's site URL? I've been Googleing to beat the band, but it doesn't turn up. Ted KX4OM Hi Ted, Plug Bill's call, N2CQR into QRZ.COM His URL is there. Dale |
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