Recommendations for base antenna to attach to APX portable

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W6VVM

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Happy Friday!

My scenario: I've got an APX 8000 which, when it goes home for the night, is just shy of system coverage. It receives while up on the roof of the house. I hope I'm being reasonable in thinking I can get this tackled within a budget of say...$150...but let me know if I'm way off.

I'm looking for a recommendation on a fairly low profile antenna (10 to 20" perhaps) and hardware that I can strap to the edge of the roof. For this purpose I'm only looking to receive right around 470 Mhz. My coax run would be under 50 ft. I'm also looking for advice on LMR400 vs RG6Q. I know I'm not providing hard data on signal strength - sorry about that. My thought is LMR400 is the safer bet but I also wonder if cable that heavy puts the radio's antenna connector at risk.

And finally, on the topic of radio damage. Any reason why this entire plan is a bad idea? The radio won't be used for Tx when this antenna is connected, but as I understand it, there is a level of transmitting that occurs automatically for the radio to affiliate when it is powered up or a channel is selected. I want to make sure there is no risk to the radio. If the stock antenna is gently transitioned back and forth once per week, will this cause excessive fatigue on the connector?

Thanks for the help!
 

jim202

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First of all, you will need the RF cable adapter for the radio. A flexible jumper from the radio to the coax cable you run to the roof antenna will prevent any damage to the radio. After that, what cable you use going to the roof is up to you as long as it is in the 50 Ohm range.
 

Thunderknight

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Make sure the antenna is designed for the band. If you are marginal on the roof, go for a yagi antenna pointed in the direction of the system...that will help make up for the loss in the coax. If it's a trunked system, the system needs to hear the radio to register.
Make sure to use 50 ohm coax. At UHF and for 50 feet, LMR-400 should work out well.
As jim202 said, USE A FLEX JUMPER at the end of the LMR-400 to go to the radio.

And of course...is your house in the licensed area of the system's FCC license and does it meet the 6.1 meter control station rules? If it's a trunked system, your radio will need to transmit. (a receiver only doesn't need to be licensed).
 

mmckenna

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APX-8000 is a tri-band radio. You can set up a tri-band antenna, but that's going to cost a bit more. If you can tell us if you only need one specific band, we could probably make some better suggestions.

If you need to do the entire tri band capability of your radio, this would probably be the way I'd do it to stick within your budget (sort of):
This antenna:
This base mount adapter:

That base mount adapter has a female N connector on it. Your LMR-400 with a male N connector will attach. Waterproof the connection properly.
Route the coaxial cable down to a point where you can enter the house. National Electric Code says you need one of these installed:
That will need to be properly grounded to your homes electrical ground system. Consult and electrician to do it correctly.

LMR-400 is fine, but as you suggested, you'll need to make the transition to the radio. Since LMR-400 is stiff, it's going to be problematic to try and connect directly to the radio. Using a short whip of thiner coaxial cable will take the strain off the connector. You can spec out custom cable here:
Female N to match the Male N on the LMR 400. Give yourself a couple of feet of the LMR-195. A female SMA connector should make the connection to the radio.

But, be aware, the connectors on the radios are not really rated for a huge number of cycles. Constantly changing antennas on the radio may lead to accelerated failure.

If it was me, I'd probably just get a scanner or pager and leave it hooked up 24x7. Put your APX in the charger at night and let it charge. Let the scanner/pager take care of the monitoring duties.
 

W6VVM

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First of all, you will need the RF cable adapter for the radio. A flexible jumper from the radio to the coax cable you run to the roof antenna will prevent any damage to the radio. After that, what cable you use going to the roof is up to you as long as it is in the 50 Ohm range.
Thank you for the advice. I wonder what adding a jumper will do to my reception but I agree it's probably a necessity.


APX-8000 is a tri-band radio. You can set up a tri-band antenna, but that's going to cost a bit more. If you can tell us if you only need one specific band, we could probably make some better suggestions.

If you need to do the entire tri band capability of your radio, this would probably be the way I'd do it to stick within your budget (sort of):
This antenna:
This base mount adapter:

That base mount adapter has a female N connector on it. Your LMR-400 with a male N connector will attach. Waterproof the connection properly.
Route the coaxial cable down to a point where you can enter the house. National Electric Code says you need one of these installed:
That will need to be properly grounded to your homes electrical ground system. Consult and electrician to do it correctly.

LMR-400 is fine, but as you suggested, you'll need to make the transition to the radio. Since LMR-400 is stiff, it's going to be problematic to try and connect directly to the radio. Using a short whip of thiner coaxial cable will take the strain off the connector. You can spec out custom cable here:
Female N to match the Male N on the LMR 400. Give yourself a couple of feet of the LMR-195. A female SMA connector should make the connection to the radio.

But, be aware, the connectors on the radios are not really rated for a huge number of cycles. Constantly changing antennas on the radio may lead to accelerated failure.

If it was me, I'd probably just get a scanner or pager and leave it hooked up 24x7. Put your APX in the charger at night and let it charge. Let the scanner/pager take care of the monitoring duties.
Thanks so much for the detailed write up. Radio would only Rx around 470 MHz while using the external antenna. The system's got partial encryption so scanner won't work.

In any case, per the below quote, it looks like there's more to consider here before proceeding.


And of course...is your house in the licensed area of the system's FCC license and does it meet the 6.1 meter control station rules? If it's a trunked system, your radio will need to transmit. (a receiver only doesn't need to be licensed).
Something I had not considered. Thank you for that. The antenna would be below 20 feet elevation but as far as the licensed area I am not sure. House is about 15 miles (line of site) from the repeater site - I'm guessing that doesn't answer the question though. I'll attempt to get more authoritative information before proceeding.
 

mmckenna

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Thanks so much for the detailed write up. Radio would only Rx around 470 MHz while using the external antenna. The system's got partial encryption so scanner won't work.
OK, a basic UHF antenna would be cheaper than mulitband antennas. And UHF is a bit more forgiving on the coaxial cable run than 700/800 would be.

Still, entirely do-able.
 
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