Antenna for VHF/UHF Monitoring

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jsnobelen

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Hello all, I recently purchased a wide-band antenna for my Uniden BC346XT scanner. The model is the Diamond SRH77CA, and I got this from the knowledgeable people at Radio World in Toronto, Ontario, Canada.

I live in the K-W area and am mainly interested in listening to the WRPS/FD EDACS 800MHz and MOH VHF fleetnet system. The stock antenna that came with the scanner actually isn't all that bad, and performs great for the EDACS 800MHz system, but doesn't perform well when it comes to the VHF MOH system, hence me purchasing a different antenna.

Not only did the SRH77CA not bode well at all for the MOH VHF system, it totally would not receive the EDACS 800. A little about my location: I mainly listen at home in the basement, but with access to a large window (not sure if this makes a difference, just pointing out so you're aware the room isn't entirely submerged underground). When driving around, the SRH77CA still doesn't perform well, but it will intermittently receive signals from the EDACAS system, and then the MOH system, but only when the unit is physically being held. Sidenote: when driving around, the stock antenna is fabulous in all areas, just not in my basement.

Hopefully I have provided enough information about my situation. My question here is what antenna(s) do you guys recommend and why? I should also mention that in my frustration (knowing I needed a longer antenna length for the longer VHF bandwidth) I grabbed a hanger out from the closest, unwound it, wrapped it around the top of the rubber duck antenna twice and ran the rest up a wall, and the MOH fleetnet came in crystal clear with signal strengths of 5. While this may be funny and work, it's tacky and I can't bring that setup into my vehicle. I need an antenna that works well in both environments, is cost effective, and still rationally sized.

I tried to provide as much information about my thinking here, if you have any questions, please fire away.

Thanks in advance for anybody's help!
 

DickH

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This is worth a try and will not cost one penny (unless your coat hanger has value) :)
Cut the coat hanger to 16-1/4" or 19-1/2" and connect it to the antenna input. Here's my reasoning. 1/4 wavelemgth at 850MHz is 3-1/4". Multiples of that length should receive your 800MHz OK and 16-1/4 and 19-1/2 will get you into the 150-160MHz VHF range. The VHF range is not as critical as the 800MHz.
Try experimenting with various lengths. You may be surprised at the results.
Of course you can also use #12 copper house wire.

Here's one of the many I have made. http://dickh.zenfolio.com/img/s10/v17/p773668180-3.jpg
 

prcguy

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Odd multiples of 1/4 wavelength can match somewhat to 50ohms but the 1 1/2 to 2 wavelength whip your proposing will be more directional off the ends at an angle, not so good.

Even multiples after 1/2 wavelength will present a high impedance to the radio and performance will suffer in addition to the directionality off the ends.

For the OP, the SRH77CA is tuned to the 146 and 446MHz ham bands and will loose some performance in the VHF and UHF commercial bands.
prcguy




This is worth a try and will not cost one penny (unless your coat hanger has value) :)
Cut the coat hanger to 16-1/4" or 19-1/2" and connect it to the antenna input. Here's my reasoning. 1/4 wavelemgth at 850MHz is 3-1/4". Multiples of that length should receive your 800MHz OK and 16-1/4 and 19-1/2 will get you into the 150-160MHz VHF range. The VHF range is not as critical as the 800MHz.
Try experimenting with various lengths. You may be surprised at the results.
Of course you can also use #12 copper house wire.

Here's one of the many I have made. http://dickh.zenfolio.com/img/s10/v17/p773668180-3.jpg
 

jsnobelen

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@DickH
@ prcguy

If someone cannot recommend an antenna they have had experience with that will work for me, I am willing to give the project a go. Thanks for the picture. Do you have one of a whip you have made? I understand your planning Dick, but according to prcguy I will need a different length for the "wire". So prcguy, what should I be doing/math should I be using?
 

kny2xb

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492 ÷ frequency = ½ wave in feet

246 ÷ frequency = ¼ wave in feet

5904 ÷ frequency = ½ wave in inches

2952 ÷ frequency = ¼ wave in inches

for example:

492 ÷ 150 MHz = 3.28 feet or 39.36 inches for ½ wave

246 ÷ 150 MHz = 1.64 feet or 19.68 inches for ¼ wave

I'm going to make one of these myself for inside use and see how it works out for improving my aircraft band reception.
 

jsnobelen

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kny2xb said:
492 ÷ frequency = ½ wave in feet

246 ÷ frequency = ¼ wave in feet

5904 ÷ frequency = ½ wave in inches

2952 ÷ frequency = ¼ wave in inches

for example:

492 ÷ 150 MHz = 3.28 feet or 39.36 inches for ½ wave

246 ÷ 150 MHz = 1.64 feet or 19.68 inches for ¼ wave

I'm going to make one of these myself for inside use and see how it works out for improving my aircraft band reception.
@ kny2xb

Thanks, please post a picture here when you're done, if you wouldn't mind, and let us know how the reception is.
 
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