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Does feed line length matter?
- Thread starter Marconi
- Start date
It could happen. I've picked up some ham amp projects that were scary. Fortunately they didn't get far enough along to start a house fire or electrocute themselves. Ignorance is bliss on all the bands.
- A lot of people miss that Resonance part...Another aspect others don't always consider in using Balun type matching - is it's multiplier effect...
Step-up ... Step-down - Step over...
Side Step, slide under.. Dosey-doh...
Another aspect others don't always consider in using Balun type matching - is it's multiplier effect...
Step-up ... Step-down - Step over...
No there isn't, that's a false claim. Losses from connectors are fractions of a dB per connector. There's a Youtube video of a guy who connects I think it is 30 connectors and adapters together of all kinds, SO239, N type, BNC with the only thing they share being they're all 50 ohm impedance and measures the output from an analyser at the other end and its not even one dB lost throughout the whole chain.
Sure some are scary but the cast majority are fine. Besides the point was not about HV issues or such other safety issues but rather input tuning and the required tuned input network versus a piece of coax cut to length to effect a matching stub.
Agreed. I missed that and had to go back after you mentioned it. For some ungodly unknown reason signal calculations always seem to like to use 1 dB per connector when determining expected signal strengths when calculating system and path losses. I had to do that MANY times when I was in commercial broadcasting. I always thought it was stupid however I guess it did give an absolute worse case scenario. I myself have strung a crap load of connectors of just about every series from UHF to BNC, F, N, mini UHF, TNC etc and despite having about two dozen connectors in series I could barely notice any losses. Even when using 5 watts for full scale deflection I would still see greater than 4 our watts after all the connectors. Insertion losses are much less than 1 dB per connector. If they were very high the connectors would heat up under high power operation.
The one that came to mind was a 20m mono bander with a light duty roller inductor for a tank coil. It was a 4cx1000. The guy would have fried that roller inductor trying to design a tank circuit with Edison guesses. He was an old timer and an rf god among his minions. Check out some qrz threads a lot of guys have trouble matching stuff. HV stuff is another matter so I won't mention that.
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I have known many Ham Operators who built their own amps and some were mono band and some were multi band and some bothered with building a tuned input and some did not.I never heard any of them mention having an issue with the length of the jumpers or feed line.
SIX-SHOOTER
OMG!
And here I catch both of you saying this...
Did you not read the post about the Co-phased antennas? Semis' use these co-phased harnesses all the time...
You guys just nixed yourself and to claim yourselves as Amateur Operators!
Call signs or not, go back to your respective corners and come out swinging with real reasons as to why...
Ok, How I feel aside, you just insulted the very essence of your existence with the total disregard to the PROPER Install and use of a harness in Co-phased arrays and their own networks!
Don't flame me until you figured that one out! (You need that length - have we forgotten? How about those antennas that use a Matching Network in order to obtain low-SWR - DC-Grounded Shunt fed-antennas would never exist!)
Connectors? Why worry? Well, you don't fix the messes I see...I answered Marconi's question about the Feed line - single antenna or Co-phased with examples of why this train of thought even exists - common' guys, you know the realm of length is there, even though we presume it can be disregarded. (We forget the fine print - If Properly Installed)
The issue of Resonance and Radiators - and the Feedpoint impedance are variables that many CB'ers or Amateurs as shown above...tend to ignored because people are too focused on SWR. So those store bought antennas are designed to handle a wide variety of installations, but none, no - not one can claim better than a Dipole - especially when you know the antennas radiators are far less in length than even a 1/4 wave whip.
However, with lower SWR, these hapless users can now offset that loss, by using far more power that replaces the wattage and field strength into this Low-SWR but lossy low-radiation-resistor of a Radial - and reap the benefits that assure the rest of us the Lengths do matter - just not necessarily referring to coax.
Refer to Owners Manual.
You guys know better!
And here I catch both of you saying this...
- Did you bother to have the Volume up enough, to hear, or at least read, the CC - it's based upon 20 Meters? Start at 3:28 ok? Use CC if you need to...
Did you not read the post about the Co-phased antennas? Semis' use these co-phased harnesses all the time...
You guys just nixed yourself and to claim yourselves as Amateur Operators!
Call signs or not, go back to your respective corners and come out swinging with real reasons as to why...
Ok, How I feel aside, you just insulted the very essence of your existence with the total disregard to the PROPER Install and use of a harness in Co-phased arrays and their own networks!
Don't flame me until you figured that one out! (You need that length - have we forgotten? How about those antennas that use a Matching Network in order to obtain low-SWR - DC-Grounded Shunt fed-antennas would never exist!)
Connectors? Why worry? Well, you don't fix the messes I see...I answered Marconi's question about the Feed line - single antenna or Co-phased with examples of why this train of thought even exists - common' guys, you know the realm of length is there, even though we presume it can be disregarded. (We forget the fine print - If Properly Installed)
The issue of Resonance and Radiators - and the Feedpoint impedance are variables that many CB'ers or Amateurs as shown above...tend to ignored because people are too focused on SWR. So those store bought antennas are designed to handle a wide variety of installations, but none, no - not one can claim better than a Dipole - especially when you know the antennas radiators are far less in length than even a 1/4 wave whip.
However, with lower SWR, these hapless users can now offset that loss, by using far more power that replaces the wattage and field strength into this Low-SWR but lossy low-radiation-resistor of a Radial - and reap the benefits that assure the rest of us the Lengths do matter - just not necessarily referring to coax.
Refer to Owners Manual.
You guys know better!
BJ radionut
Supporting Member and 6m addict
A few common tubes have a cathode impedance near 50 ohms and I've heard of them being used with no tuned input. From what I understand that is not good practice, but I'm no expert.
I think it was rich measures that explained the flywheel effect and why a tuned input is desirable. A tuned input is cheap and easy to build with scrap parts.
I suppose you could use the same circuit for a transistor amp to fine tune it. That's something I've wanted to try but never did. It might be worth looking at the schematic for the 2879 amp that mfj made or a Henry 750. There aren't many hams that I know of building bipolar transistor amps.
I just love it when an ass hole makes himself look like an even BIGGER ass hole like you just did. First you insult me and then berate me for doing or not doing something and in fact YOU missed my posts where I actually DID mention about proper lengths NEEDING to be used in phased systems. Instead of ME needing CC and comprehending it was on 20m perhaps YOU need to have a Braille touch screen because obviously you are blind to add to your ignorance.
AS for not worrying about the connectors......WTF are you talking about. READ what I said AGAIN. This time pay attention. I have done the same experiment on 450 MHZ and saw VERY LITTLE power loss. As for fixing messes.......22 years in the engineering shop of a commercial broadcasting station working with everything from DC to daylight DID on fact see me fixing quite a few messes from people before me. AS for messes I have repaired three phase HV power supplies on the DC end and installed lightning damaged 1.7 GHz gear and feedlines along with fried heliax from the AM and FM transmitters. YES I have fixed MANY messes so don't sit there and berate ME until you KNOW WHO I AM AND WHAT MY EXPERIENCE HAS BEEN.
As for your next reply I suggest you consider the wording VERY carefully.
Too much drama. We almost had a good thread.