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dipole length vs db
hi
I ponder once again , and got a bit confused : Currently i have a centerfed horiz dipole up pretty high it's total length is less than 40ft, center feed via my sgc i was thinking it'd be nice to have a SIGNIFICANT /real order of magnatude type improvement in 'performance' or gain my thought therefore went to making the dipole longer (as it's kinda on the short side now) so given the effort involved i wonder how much longer do i have to make it to really extract a sig difference? thanks m |
dipole length vs db
There are lots of factors to consider here. On the bands where your
antenna is longer than a half wavelength dipole, it will show gain over the equivalent dipole. If you keep it about 40 feet, it will have a single main lobe all the way up to 10m, where it's getting close to being an extended double zepp (two 5/8ths wave halves) If you make it much longer, the pattern will break up into multiple lobes on the highest bands (which can, but not always will be, higher gain, but in weird directions, and there will be deep nulls) Of course, the higher bands (10, 12, to a certain extent 15) are dead these days, so maybe we can exclude them from consideration. - - - - - The other thing to look at is the matching efficiency on the LOW bands. The antenna is very, very short for 160 and 80m and is quite short for 40m operation. The tuner, if it will give you a match at all, isn't going to be operating as efficiently as it could when you're operating on the lower frequencies. Lengthening the antenna would help that, and in that case, the gain could change a LOT, in the sense that you'd have a lot less LOSS. So it depends on what you want to do. If you're doing a lot on 80m and 40m, and want to have a dipole-like pattern all the way up to 17m, I would suggest making the antenna maybe 74 feet total or so. This will still put the 17m main lobe broadside to the antenna like a dipole (though with some nonnegligible secondary lobes, but that's OK) and will do much better on 80m as far as the tuner's ability to match. The multi-lobed nature on 15, 12, and 10 wouldn't ruin all operation there. - - - - - If you want to get gain in a particular direction using just a single wire, you need phasing sections, but that gain isn't all that useful unless you have a particular narrow direction that you favor, and your gain would be single-band anyway. So what you gain by lengthening a straight wire is more that you'll have *less loss* on the lower bands, not so much that you'd get gain on the higher bands (though a 74 foot doublet does have about 2.5dB gain over a 1/2 wave dipole on 17m), and if you're trying to use a 40 foot dipole on, say, 80m, you could expect many dB of improvement by moving to a longer antenna. Dan |
dipole length vs db
thanks very much for taking the time to help me out dan, appreciate it
some of what you wrote sorta confused me, and maybe some left me wondering still i see what you ment about adding length improving the lower frequencies 80m i am 'ok' with that but if I made the antenna length for ex 74' it's 'bad' or sort of less than ideal things would happen on say 10m??? meaning it would be 'too' long? so my goal here was an extreem gain 2orders of magnatude at least i sorta thought that perhaps a wave on the lowest freq (160)might be ok, but i get confused on how say that would negatively effect 10m as the lobes increse their the penality is lots of nulls and radating in odd directions? so if i was listening to 10m and a sig was comming in on my existing antenna say s9 and i made the antenna 74ft the signal would be lower? maybe? if this is true to get an 'optimal' all bad dipole you'd have to have say 2 of them a 160-40 another for the rest? just a little confused In article .com, " wrote: There are lots of factors to consider here. On the bands where your antenna is longer than a half wavelength dipole, it will show gain over the equivalent dipole. If you keep it about 40 feet, it will have a single main lobe all the way up to 10m, where it's getting close to being an extended double zepp (two 5/8ths wave halves) If you make it much longer, the pattern will break up into multiple lobes on the highest bands (which can, but not always will be, higher gain, but in weird directions, and there will be deep nulls) Of course, the higher bands (10, 12, to a certain extent 15) are dead these days, so maybe we can exclude them from consideration. - - - - - The other thing to look at is the matching efficiency on the LOW bands. The antenna is very, very short for 160 and 80m and is quite short for 40m operation. The tuner, if it will give you a match at all, isn't going to be operating as efficiently as it could when you're operating on the lower frequencies. Lengthening the antenna would help that, and in that case, the gain could change a LOT, in the sense that you'd have a lot less LOSS. So it depends on what you want to do. If you're doing a lot on 80m and 40m, and want to have a dipole-like pattern all the way up to 17m, I would suggest making the antenna maybe 74 feet total or so. This will still put the 17m main lobe broadside to the antenna like a dipole (though with some nonnegligible secondary lobes, but that's OK) and will do much better on 80m as far as the tuner's ability to match. The multi-lobed nature on 15, 12, and 10 wouldn't ruin all operation there. - - - - - If you want to get gain in a particular direction using just a single wire, you need phasing sections, but that gain isn't all that useful unless you have a particular narrow direction that you favor, and your gain would be single-band anyway. So what you gain by lengthening a straight wire is more that you'll have *less loss* on the lower bands, not so much that you'd get gain on the higher bands (though a 74 foot doublet does have about 2.5dB gain over a 1/2 wave dipole on 17m), and if you're trying to use a 40 foot dipole on, say, 80m, you could expect many dB of improvement by moving to a longer antenna. Dan |
dipole length vs db
ml wrote:
but if I made the antenna length for ex 74' it's 'bad' or sort of less than ideal things would happen on say 10m??? meaning it would be 'too' long? Too long for what? Horizontal long wire antennas have certain radiation characteristics. Consider the rhombic. Some say it's the best antenna in the world. so my goal here was an extreem gain 2orders of magnatude at least i sorta thought that perhaps a wave on the lowest freq (160)might be ok, but i get confused on how say that would negatively effect 10m as the lobes increse their the penality is lots of nulls and radating in odd directions? Sometimes "odd" directions are the best if that's the direction of your desired contact. My own 130 foot dipole works like gangbusters on 17m. It has 8 lobes each at about 8 dBi with a take-off- angle of 19 degrees. so if i was listening to 10m and a sig was comming in on my existing antenna say s9 and i made the antenna 74ft the signal would be lower? maybe? Maybe lower but maybe higher. Unknown directions for horizontal antennas may be good. The g5rv designer, Mr. Varney, deliberately designed his 20m dipole to be "too long" because he desired the multi- lobed radiation pattern. -- 73, Cecil http://www.w5dxp.com |
dipole length vs db
thanks cecil, i kinda didn't fully understand some things in dan's post my overalll takeaway was that just adding length to the antenna might be 'bad' ie not really garantee full band tremendious signal improvements 160m-10m in the same direction as i radiate now (mostly e-w) from his post maybe he might add a few more comments to see how i can add length and non direction gain to my setup on the higher freq side as well as the lower but i understood what you wrote cecil i think for me to just try it might be most fun perhaps w/a switch In article , Cecil Moore wrote: ml wrote: but if I made the antenna length for ex 74' it's 'bad' or sort of less than ideal things would happen on say 10m??? meaning it would be 'too' long? Too long for what? Horizontal long wire antennas have certain radiation characteristics. Consider the rhombic. Some say it's the best antenna in the world. so my goal here was an extreem gain 2orders of magnatude at least i sorta thought that perhaps a wave on the lowest freq (160)might be ok, but i get confused on how say that would negatively effect 10m as the lobes increse their the penality is lots of nulls and radating in odd directions? Sometimes "odd" directions are the best if that's the direction of your desired contact. My own 130 foot dipole works like gangbusters on 17m. It has 8 lobes each at about 8 dBi with a take-off- angle of 19 degrees. so if i was listening to 10m and a sig was comming in on my existing antenna say s9 and i made the antenna 74ft the signal would be lower? maybe? Maybe lower but maybe higher. Unknown directions for horizontal antennas may be good. The g5rv designer, Mr. Varney, deliberately designed his 20m dipole to be "too long" because he desired the multi- lobed radiation pattern. |
dipole length vs db
ml wrote:
but i understood what you wrote cecil Walter Maxwell's advice is to make the dipole at least 3/8 wavelength on the lowest frequency of operation, feed it with ladder-line through a 1:1 choke, and enjoy. -- 73, Cecil http://www.w5dxp.com |
dipole length vs db
In article , ml wrote:
Currently i have a centerfed horiz dipole up pretty high it's total length is less than 40ft, center feed via my sgc i was thinking it'd be nice to have a SIGNIFICANT /real order of magnatude type improvement in 'performance' or gain ML- I have a similar question, but I'm not looking for a "real" order of magnitude improvement. I just want to get on the air. If I only have room for a short dipole, say 40 feet, and use a tuner such as the SGC or Icom AH-4, what is the penalty in DB for the lower bands (160, 75, 60, 40) compared to a half wave on each band? 73, Fred K4DII |
dipole length vs db
Fred McKenzie wrote:
If I only have room for a short dipole, say 40 feet, and use a tuner such as the SGC or Icom AH-4, what is the penalty in DB for the lower bands (160, 75, 60, 40) compared to a half wave on each band? Don't know the dB but losses would be appreciable. Why not put up a 22 foot vertical with a good radial system? That will work pretty well for 40m-10m using the autotuner at the base. Install a base loading coil and it will work reasonably well on 75m. Can't say much for 160m. -- 73, Cecil, http://www.qsl.net/w5dxp |
dipole length vs db
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dipole length vs db
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dipole length vs db
In article , ml wrote:
If I only have room for a short dipole, say 40 feet, and use a tuner such as the SGC or Icom AH-4, what is the penalty in DB for the lower bands (160, 75, 60, 40) compared to a half wave on each band? 73, Fred K4DII just a fyi, this really belongs in a new thread ML- Perhaps you are right. I was attempting to ask the same question in reverse: The "penalty" is the opposite of the possible improvement. So far I've learned that the majority of loss is in the matching network. Actual gain of a shortened dipole is only about a half dB down, but radiation resistance is so low that I-squared-R losses in the tuner are significant. Someone mentioned that you could reduce losses in the tuner by adding external loading coils. It seems to me that you would just be moving the loss out of the tuner into the loading coils. The question of whether an order of magnitude of improvement can be attained appears to be answered. If you define that as ten dB of improvement, then probably not. The total penalty is most likely less than that. 73, Fred K4DII |
dipole length vs db
On Thu, 12 Oct 2006 23:30:17 -0400, (Fred McKenzie)
wrote: So far I've learned that the majority of loss is in the matching network. Actual gain of a shortened dipole is only about a half dB down, but radiation resistance is so low that I-squared-R losses in the tuner are significant. You are right that the gain of a short practical dipole is good (and that requires that the losses are low). The transmission line is a potential source of high loss when feeding a short dipole. There was an article on QST some time back on using a 66' dipole on all bands. I have written a review which contains some graphs that cast light on where the losses are, the article is at http://www.vk1od.net/LOLL/index.htm . It turns out that for most practical configurations, it is difficult to achieve good overall efficiency when the dipole length is below about 35% of a wavelength. You will probably need parallel wire transmission line rather coax for a shortened dipole. Someone mentioned that you could reduce losses in the tuner by adding external loading coils. It seems to me that you would just be moving the loss out of the tuner into the loading coils. The question of whether an order of magnitude of improvement can be attained appears to be answered. If you define that as ten dB of improvement, then probably not. The total penalty is most likely less than that. Taking an "order of magnitude" to mean a tenfold increase or decrease (10dB), it will be challenging to improve an antenna tenfold by just adding length unless it was very inefficient in the first place (too short, lossy feedline + ATU). If you coax centre fed a 40' dipole on 3.6MHz with 30m of RG58, you would find opportunity for tenfold improvement by increasing length (to a particular value).... but only because it was so hopelessly inefficient as configured. By my 35% suggestion, a typical parallel line centre fed 40' dipole will peform ok down to about 8.6MHz. If it is coax fed, it will only be reasonably efficient on its series resonances (~12MHz, ~36MHz). Owen -- |
dipole length vs db
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dipole length vs db
ml,
I think the other posters have covered the fact that you just can't get an order of magnitude or two over all bands just by lengthening the wire. Two orders of magnitude, or 20dB gain over a dipole requires really heroic effort in antenna building at HF. If you put a lot of time, money and effort into it, you might be able to get 20dB gain over a dipole on 10 meters. You would have to use stacked long-boom beams or something of that sort. Even 10dB gain over a dipole is going to require a big beam. Think 5 element yagi or so. So, unfortunately, you're not likely to get a gain of more than a few dB over a dipole... maybe 5 or 6dB, like Cecil's antenna on 17m, which is a substantial gain, but falls short of an order of magnitude. Cecil's point is valid. I went a bit overboard on saying that the pattern of a long dipole was BAD. The multiple lobes can be useful if they point in the directions you want to work, it's true. It IS bad if there happens to be a null on a station you want to work. It's good to be able to put the energy you're radiating in the direction you want. For a long multiband antenna you can't rotate, this could be hard because the direction of the peaks and nulls changes with frequency. This could be good, it could be bad, but without pictures, you just don't know which way your signal is going. (you can find some pictures of long doublet patterns here, by the way: http://www.cebik.com/wire/abd.html.) - - - - - - Something to think about regarding massive signal improvement from changing your antenna: Having a high gain antenna means that you get response in the direction you want *at the expense* of other directions. This is why high gain ham antennas are made rotatable. You can send all your transmitted power in a narrow *beam* in the direction you want to work. For a very long doublet, the lobes may have gain over a dipole, and that could certainly be useful for some contacts. It could be, though, that you have a null in the direction you want to work. In the end, that probably all averages out. - - - - - - If the multiple-lobed pattern works for you, just make the antenna 1/2 wavelength long on the lowest frequency of operation. This will give you a big EFFICIENCY boost on the low frequencies, because less of your power will go to heat in the tuner. I wonder, also, how high your antenna is above ground. Putting your antenna higher will improve the signal on all bands, possibly dramatically on the lower frequencies if it's not up at least an eighth to a quarter of a wavelength on the lowest band. You might just try to build something for a single band where you want improvement. That's what I did when I was starting out. I had a 150 foot wire that I used on all bands, but then I started building single band antennas for my favorite bands to improve performance there. 73, Dan |
dipole length vs db
If I only have room for a short dipole, say 40 feet, and use a tuner such
as the SGC or Icom AH-4, what is the penalty in DB for the lower bands (160, 75, 60, 40) compared to a half wave on each band? Some quasi-wild guesses for a 40 foot dipole relative to full size at the same height, probably best case. 160m: -16dB 75m: -8dB 60m: -3dB 40m: -1.5dB These numbers don't mean much. I used EZNEC to look at the losses in Q=100 loading coils with enough reactance to bring thing to resonance on each band. No attempt to match to 50 ohms was made, but I made the Q kind of low to reflect other tuner losses. Still, these are almost certainly optimistic, especially on 160. Dan |
dipole length vs db
On 12 Oct 2006 23:32:20 -0700, "
wrote: If I only have room for a short dipole, say 40 feet, and use a tuner such as the SGC or Icom AH-4, what is the penalty in DB for the lower bands (160, 75, 60, 40) compared to a half wave on each band? Some quasi-wild guesses for a 40 foot dipole relative to full size at the same height, probably best case. 160m: -16dB 75m: -8dB 60m: -3dB 40m: -1.5dB These numbers don't mean much. I used EZNEC to look at the losses in Q=100 loading coils with enough reactance to bring thing to resonance on each band. No attempt to match to 50 ohms was made, but I made the Q kind of low to reflect other tuner losses. Still, these are almost certainly optimistic, especially on 160. Dan, looking at a hypothetical unloaded scenario... I don't know what feedpoint Z you got for a centre fed 40' dipole at 7MHz... but lets guess somewhere about 11+j750. Lets feed the antenna with 15m (~50') of RG58C/U for a loss of 18dB (efficiency 1.6%) and an input z at the ATU of 44-j179. The ATU should handle that with very low loss... so overall, the efficiency is ~1.6%. You can do these calcs with the line loss calculator at http://www.vk1od.net/tl/tllc.php, nothing to unzip! Adding 26' of wire to the dipole should improve the antenna to better than 80% efficiency or a fifty fold improvement on transmit. But it only worked so dramatically because the 40' dipole centre fed with coax is so inefficient. Owen -- |
dipole length vs db
On Fri, 13 Oct 2006 06:51:50 GMT, Owen Duffy wrote:
7MHz... but lets guess somewhere about 11+j750. Lets feed the antenna Spellcheckers aren't smart enough, should read: 7MHz... but lets guess somewhere about 11-j750. Lets feed the antenna -- |
dipole length vs db
Fred McKenzie wrote:
Someone mentioned that you could reduce losses in the tuner by adding external loading coils. It seems to me that you would just be moving the loss out of the tuner into the loading coils. Very little radiation occurs before the tuner. Lots of radiation often occurs between the feedpoint and the loading coils. -- 73, Cecil http://www.w5dxp.com |
dipole length vs db
thanks for the tips appreciate your time in writing the posts :)
my antenna is about 150ft high and rather higher above average terran i am up on a naturall high spot almost a hill the view from the roof is amazing only 1 other building is taller than me for miles i had thought i dunno why that if i ended up w/a dipole that was very long (multi waves) i would get increased gain(significat) at some point but i certainly dont want to end up w/directional gain i wanted a broad freq and broad radation since i like to work all bands and all locations so i learned i still can't have my cake and eat it too stomp i'll prob just follow cecil's and richards' rule, of build it and experiment i'll end up w/a 160m long dipole as it's my lowest freq and see how it goes i'll have to call my tuner manuf as i don't think it will tune that long perhaps i can modify it or i'll have to use a tuner in the shack then i'll just see how it works i guess ok on the lower part but up around 10m if i understand it i'll become more directional an a/b switch and i'll be set i'll have to figure what wire ga will support itself at that length 2 160m runs is big i can support it in the middle on one side but the other is free thanks very much i really did learn alot m In article . com, " wrote: ml, I think the other posters have covered the fact that you just can't get an order of magnitude or two over all bands just by lengthening the wire. Two orders of magnitude, or 20dB gain over a dipole requires really heroic effort in antenna building at HF. If you put a lot of time, money and effort into it, you might be able to get 20dB gain over a dipole on 10 meters. You would have to use stacked long-boom beams or something of that sort. Even 10dB gain over a dipole is going to require a big beam. Think 5 element yagi or so. So, unfortunately, you're not likely to get a gain of more than a few dB over a dipole... maybe 5 or 6dB, like Cecil's antenna on 17m, which is a substantial gain, but falls short of an order of magnitude. Cecil's point is valid. I went a bit overboard on saying that the pattern of a long dipole was BAD. The multiple lobes can be useful if they point in the directions you want to work, it's true. It IS bad if there happens to be a null on a station you want to work. It's good to be able to put the energy you're radiating in the direction you want. For a long multiband antenna you can't rotate, this could be hard because the direction of the peaks and nulls changes with frequency. This could be good, it could be bad, but without pictures, you just don't know which way your signal is going. (you can find some pictures of long doublet patterns here, by the way: http://www.cebik.com/wire/abd.html.) - - - - - - Something to think about regarding massive signal improvement from changing your antenna: Having a high gain antenna means that you get response in the direction you want *at the expense* of other directions. This is why high gain ham antennas are made rotatable. You can send all your transmitted power in a narrow *beam* in the direction you want to work. For a very long doublet, the lobes may have gain over a dipole, and that could certainly be useful for some contacts. It could be, though, that you have a null in the direction you want to work. In the end, that probably all averages out. - - - - - - If the multiple-lobed pattern works for you, just make the antenna 1/2 wavelength long on the lowest frequency of operation. This will give you a big EFFICIENCY boost on the low frequencies, because less of your power will go to heat in the tuner. I wonder, also, how high your antenna is above ground. Putting your antenna higher will improve the signal on all bands, possibly dramatically on the lower frequencies if it's not up at least an eighth to a quarter of a wavelength on the lowest band. You might just try to build something for a single band where you want improvement. That's what I did when I was starting out. I had a 150 foot wire that I used on all bands, but then I started building single band antennas for my favorite bands to improve performance there. 73, Dan |
dipole length vs db
Owen Duffy wrote:
On Fri, 13 Oct 2006 06:51:50 GMT, Owen Duffy wrote: 7MHz... but lets guess somewhere about 11+j750. Lets feed the antenna Spellcheckers aren't smart enough, should read: 7MHz... but lets guess somewhere about 11-j750. Lets feed the antenna -- Hahaha... guess you need a complex conjugation checker. Owen, I was assuming no feedline and an antenna tuner at the feedpoint and being very gracious towards that antenna tuner's abilities ( I wouldn't be surprised if a tuner could match 11-j750 with 1.5dB of loss, though maybe not a 100W-class autotuner). As far as the transmission line calculator goes, I use it ALL the time. It's a fantastic resource, both technically and ... well, rhetorically. A lot of folks will say their antenna works even if their antenna is a 40 foot dipole fed with 50 feet of RG-58 on 40m. They can hear people with it, their rig's autotuner loads it up just fine on 40m, and they can "make contacts" but their effective radiated power is going to be 1.6 watts... and feedline loss is an environmentally-unfriendly way to be a QRP operator. Dan |
dipole length vs db
ml wrote:
i'll end up w/a 160m long dipole as it's my lowest freq and see how it goes For the 160m band, the antenna only needs to be 80m long. The rule is: Make the dipole 1/2WL long on the lowest frequency of interest. And actually, using a tuner, you can get away with making it 3/8WL long on the lowest frequency of interest. So your dipole only needs to be ~60m long to cover 160m-10m. -- 73, Cecil http://www.w5dxp.com |
dipole length vs db
On 13 Oct 2006 05:34:13 -0700, "
wrote: Dan, locating the tuner at the feedpoint is certainly a method of reducing feedline loss. You will need very long arms or a remote automatic tuner. I have been surprised by how slow the market has been to match / excite the potential demand for a remote auto-tuner with balanced output (I think SGC does one, but I have no idea of how it performs). Otherwise, the feedline is critically important in antenna system performance, and you can only determine that by analysing the entire system as a system. .... rhetorically. A lot of folks will say their antenna works even if their antenna is a 40 foot dipole fed with 50 feet of RG-58 on 40m. They can hear people with it, their rig's autotuner loads it up just fine on 40m, and they can "make contacts" but their effective radiated power is going to be 1.6 watts... and feedline loss is an environmentally-unfriendly way to be a QRP operator. Yes, but note that 20dB of feedline loss on 40m probably does not degrade the receive signal to noise ratio because even when external noise is decreased by 20dB, it still swamps the receivers internal noise, and signal to noise ratio is dominated by the (external) signal and external noise (both attenuated). For example, if you look at Fig 2 at http://www.vk1od.net/fsm/FSAmbientNoise.htm you will see that expected ambient noise power in 2kHz bandwidth on 7MHz is somewhere in the range -87dBm to -108dBm, with somewhere above -103dBm (~S4) being typical in a good location. Attenuating noise at -103dBm by 20dB gives -123dBm, still way above the noise floor of modern receivers at about -135dBm. So from a rx perspective, it "works", demonstrated by copying other stations ok, just the S-meter reading is low. One of our new Foundation Licencees asked me a question through a site feedback form some months age. It is relevant to this issue in a near QRP context, FLs are limited to 10W PEP on SSB, 3W carrier on other modes. Foundation Licencees qualify with about 6 hours of training, mostly on operational practice and very little technical content. The question and my response are below: Question: Why can't I get contacts on 80m. I don't have room for an 80m dipole, so I am using my 40m dipole that works just great on 40m. Of course, it would not be impedance matched on 80m, so I have used an ATU (which I was taught matches the antenna and line to the transmitter) and can easily get SWR of 1:1 (excellent match!). My antenna is fed with 25m of RG58C/U as an expert told me that it has a loss of only 0.6dB and I wouldn't notice that. Answer: It is true that the loss on 25m of RG58C/U on 80m under matched line conditions is about 0.6dB and for most purposes that might be quite acceptable. For reasons beyond your current understanding, your line is not matched, and the loss on your coax is much more than 0.6dB (about 15%), the losses are around 21dB (about 99.3%) and around 0.7% of your 10W output is reaching the antenna feed point. The good news is that the gain of your shortened antenna is still quite good, and your ERP (you learned about ERP for your licence) is probably around 0.1W (EIRP) broadside to your shortened dipole. If for instance you were trying to work another station that is using a 100W transmitter and an antenna system efficiency of better than 75% (realistic), their ERP is probably around 120W (EIRP). To an independent observer who hears you both above the noise and has equally good propagation from both of you, your signal is 5 S-units lower than the other station. That disparity will make it very hard for you to work all but the very strongest of stations because of the ambient noise level, and even then they will be straining to hear you in the noise. Your antenna efficiency will not as seriously impact your receive performance, because both the external noise and the desired signals are attenuated by the same amount, and are still well above the receiver's internal noise. The signal / noise ratio will be similar to using an efficient antenna, just the S-meter reading will be lower. When you run less power than the other stations that you want to work, the performance of your antenna becomes even more important. Owen -- |
dipole length vs db
"note that 20dB of feedline loss on 40m probably does not
degrade the receive signal to noise ratio because even when external noise is decreased by 20dB, it still swamps the receivers internal noise, and signal to noise ratio is dominated by the (external) signal and external noise (both attenuated). " Yeah. This is the counter-argument to "if you can hear 'em you can work 'em" Mismatched line loss needs to be covered on the entry level tests. Heck, I think they should give it two questions. It's a major issue in setting up your first station because all the tuners have two or three SO-239 jacks and one "random wire/balanced line" output. Same with the radio, tuner inside, coax connection outside. Who knows better than the engineers that built the stuff, you know? Well, I don't know if I've converted anyone yet but I often point people to this page: http://www.n3ox.net/projects/servo It's the electromechanical equivalent of having long arms, and it's ALMOST cheap.. I hope to inspire a few folks who've dropped a bunch of money on a nice tuner before they discovered the tuner-at-the-feedpoint advantage, though there are a couple of snags to work out before it's a tuner add-on that anyone can build. I need to figure out something better than 10 turn pots because they're hard to get and kind of pricey, and MFJ, who seems to sell all of the budget tuners, has stopped selling switched-inductor high power tuners. You can still get them in the "300W" class, but no more of the "1500W" ones. I'm not even using the remote tuner at the moment. I've rolled my own fixed L networks for matching my 20m delta loop on 20 and 17 and my 40 foot vertical on 80,60,40, and 30. The remote tuner served me well for the apartment doublet but I like the faster bandswitching with the switched networks. I thought about making fixed, switched networks for the wire I had up at the apartment, but it was 30 gauge wire and broke too often, and I couldn't really control the exact length of wire I was putting up every time, so the tuner really was a better solution. I do a lot of band hopping while I'm on the air (DXing, mostly) so retuning all the time was something I wanted to avoid in the new installation. Dan |
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