VHF and 800 - Yagi or discone? Same repeater site formvoth

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dimab

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I’m listening to 2 analog freqs, VHF and 800 range. I’d like to get a better signal to noise ratio as the audio is noisy at times.
Both freq are broadcast from the same tower.
Will a Yagi antenna improve my reception? I’m not clear if a Yagi is designed for multiple freq ranges.
 

jonwienke

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No. Yagis are generally single-band. If you want to pick up VHF and 800 with a single antenna, you want a discone.
 

cpfinlay

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There are several commercial dual-band yagis, but those are generally cut/spaced for 2m/70cm amateur radio (144mhz/440mhz) which would not work well for your use case.
 

Ubbe

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What antenna are you using now and where have you put it? Can you use a roof antenna or outside of the window if it faces the tower?

Sometimes a UHF yagi can perfom better than a standard VHF 1/4 wave GP antenna even if the frequency are in a different band. As you have both frequencies from the same tower it could work if you try a cheap 800Mhz yagi so you don't have to waste too much money if it fails.

If you have a portable scanner you can connect the antenna directly to your scanner and test it at different locations and if you end up on the roof and it works there, you then get RG6 coax that have low loss, it doesn't matter much for VHF but you don't want to kill the 800Mhz reception by using RG58 or other high loss coax.

/Ubbe
 

iMONITOR

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I’m listening to 2 analog freqs, VHF and 800 range. I’d like to get a better signal to noise ratio as the audio is noisy at times.
Both freq are broadcast from the same tower.
Will a Yagi antenna improve my reception? I’m not clear if a Yagi is designed for multiple freq ranges.
What are you using now? Indoors, outdoors? How high?
 

mmckenna

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1/4 wave mobile antenna on the roof of my house.
I think I'd try a multiband vertical first. A log periodic would work, but reception of systems not in the path of a log periodic will suffer. If the 1/4 wave works on VHF, adding a multiband that will cover 800 will have a bit of improvement.

If current performance is close to being good, you might be able to improve it by raising it up higher and upgrading your coaxial cable.

If not, a L-P might be a good choice.
 

Ubbe

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You mentioned that you monitor one 800Mhz and one VHF frequency. Which one are the noisy one and to what frequency are the 1/4 tuned to?

We had our old police system at 410MHz for the city police and at 79MHz for the region and a 5/8 coliniar vertical with a coil in the middle for 410MHz happened to also work as a 1/4 wave at 79MHz. So it you get a gain antenna for 800MHz it might also increase your VHF reception. Do you have the exact frequencies for the two systems so it might be possible to see if there's a 800Mhz antenna that also resonates at your VHF frequency?

How long is that coax and what type is it?

/Ubbe
 

jonwienke

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If you're absolutely sure the VHF and 800 freqs are transmitted from the same location, a log-periodic antenna covering both bands is a good option. But only if you don't care about receiving anything else. You'll only get reception in the direction the antenna is pointed.
 

prcguy

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A typical scanner type log would not have a super narrow beam width, more like 45 to 90 degrees depending on gain, so it will pick up a fairly wide swath either side of the target location.

If you're absolutely sure the VHF and 800 freqs are transmitted from the same location, a log-periodic antenna covering both bands is a good option. But only if you don't care about receiving anything else. You'll only get reception in the direction the antenna is pointed.
 

Ubbe

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If you look at Creat's log period antenna it has such a huge frequency range that it doesn't have much gain left. It's only 2 or 3 elements that resonates at a frequency and it has almost a 180 coverage in front of the antenna and certainly 90 degree with full signal.

/Ubbe
 
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