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Mobile Antenna Tuning Advise. Not happy so far
- Thread starter Charlie Brown
- Start date
magic cure, move the antenna .
when i put my wilson 5k thru the roof i used my mag mount to find the sweet spot ,and it was not the center of the roof .
it was actually more towards the front .
i know the center seems like the best place and it is for omnidirectional signal but its not always the best place swr wise .
for years i ran my wil5k mag mount in the center of the roof ,it wasnt until i got a bird meter and started reading the reflect readings that i soon realized it was not my optimal spot .
good luck brown
That has a lot of credence. It'll never be optimal in an omnidirectional way anyway on a pick up unless the centre of the roof of the cab is in the direct centre of the middle of the whole vehicle. The centre of the roof is always more towards the front of the vehicle.
And reflected readings will be skewed somewhat by metal in the vicinity of the antenna. It'll be very rare that two installs are identical.
In the end its a bit of a compromise and balancing act. For example tonight I've been tuning repeater cavities for a trunking system. Because of the range between the highest and lowest RX frequencies the cavities are running at their absolute limit for bandwidth. I've had to trade off insertion loss for attenuation of the nearest TX frequency.
Tuning for the least insertion loss across the board for RX resulted in 50dB attenuation for the TX frequency. Sacrificing 0.5dB of insertion loss resulted in an extra 10dB of attenuation for the TX frequency. The receiver won't notice an extra half a dB loss in RX but it would notice an additional 10dB of interference from the repeater output.
And reflected readings will be skewed somewhat by metal in the vicinity of the antenna. It'll be very rare that two installs are identical.
In the end its a bit of a compromise and balancing act. For example tonight I've been tuning repeater cavities for a trunking system. Because of the range between the highest and lowest RX frequencies the cavities are running at their absolute limit for bandwidth. I've had to trade off insertion loss for attenuation of the nearest TX frequency.
Tuning for the least insertion loss across the board for RX resulted in 50dB attenuation for the TX frequency. Sacrificing 0.5dB of insertion loss resulted in an extra 10dB of attenuation for the TX frequency. The receiver won't notice an extra half a dB loss in RX but it would notice an additional 10dB of interference from the repeater output.
You forgot one.
6. Gaining an understanding of the difference between reality and common hearsay regarding obtaining the ultimate 1:1 match.
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HF (3-30 MHz) Mobile Antenna, TURBO-5000, PERFORMER-5000
- SWR @ res. freq.: ≤ 1.2
Oh well,I try to get close to perfection as I can.
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Perfection is only a state of mind and not a state of reality. Those that have been into radio a long time know when good is good enough and have the logbooks/QSL cards to prove it. Whatever did the lowly operator do before SWR meters were invented or before the word "impedance" meant anything? Oh yeah....they made thousands of contacts using less than ideal and usually homebrew equipment and antennas "tuned" by watching an RF current meter for a peak or watching a light bulb coupled to the final tank coil for maximum brightness. Perfection? Nahhh....just a sense of what works and what doesn't. Life is too short to strive for that mythical "perfection" thing.
Some whizzo amp builders say your SWR has to be below 1.1:3. Maybe he's gonna run one of them "famous" amps.
- SWR @ res. freq.: ≤ 1.2
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Installed properly, the resonant frequency of the antenna which is where X=0, will be slightly lower than where the lowest SWR reading is.
Stop worrying.
Just trying to appease the radio gods,that's all. Also,I'm glad that I could get my setup perfect(my requirements) with no high swr anomalies. Backstroke,backstroke,backstroke.
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Captain Kilowatt, you hit the nail on the head. If you are making contacts and not having any issues other than a 1.3 swr, you will be fine, get out there and start talking and see what happens before you go overboard trying to get a perfect swr reading. Make some contacts locally and ask them what your readings are and log them, this way if you do decide to try for a perfect swr, you can see what kind of difference it really made. My guesses that no one will ever notice the difference. God bless and Happy Holidays.
Lol, because they are over-stressing the transistors with voltage or drive and know that things will go pop if there is any reflect.
You might find it hard to believe but I have run a T/S 500 into a SWR of 2:1 before with no ten ohm smoke......
There are some water-gates here on the forum where I was testing antennas on several bands working into that SWR with no ill effects.
Anything below 1.5:1 is nothing to worry about unless you are already stressing the transistors in some other way.
73
Jeff
