Foldable Rubber Duck?

[Seven-Delta-FortyOne]

I'm looking for an antenna like this, except in 460MHZ range.

MFJ Enterprises Inc.

Yes, I tried google, they don't seem to carry one.

What I'm trying to do, in case anyone has a better idea, is set up a very low power GMRS base station.

We use GMRS at the ranch, and the "base station" at this time is just a Kenwood TK-380. Works fine, except I am constantly charging the battery, and then is has to be taken out of service for 2 hours.

I have a couple TK-880H radios, with power supply and cabinet, and 5/8 wave base antenna. Works great, I just don't need to be transmitting daily ranch activities all over 3 counties, (I'm up on a hill).

The TK-880H will only turn down to 10 watts, so inside a house, with a rubber duck will be about perfect.

If I could use an inline attenuator, and put out about 1 watt ERP from the base station antenna, that would probably work as well. I don't know anything about reducing signals, however. I'm always doing the opposite.


Thanks for any help or suggestions.



Delta

 

[DJ11DLN]

Coaxial Adapter, BNC Female / UHF Male (PL259) - BA50

I'd get one of these and use a BNC 90 on the back of it and just use any old duck made for the correct frequency range. I don't know how well what you're describing is going to work but that's where I'd start.

 

[mmckenna]

Running a rubber duck antenna off the back of a mobile will probably lead to high SWR, which may lead to improper operation of the radio. While I understand you want to reduce the coverage, you do want to keep things working properly.

Some options:
1/4 wave ground plane antenna. (easy to make yourself)
Small mag mount with a 1/4 wave
Small mag mount with a rubber duckie antenna

 

[Seven-Delta-FortyOne]

Coaxial Adapter, BNC Female / UHF Male (PL259) - BA50

I'd get one of these and use a BNC 90 on the back of it and just use any old duck made for the correct frequency range. I don't know how well what you're describing is going to work but that's where I'd start.

That might work, but I'd have to get a PL-259 90 degree.

Running a rubber duck antenna off the back of a mobile will probably lead to high SWR, which may lead to improper operation of the radio. While I understand you want to reduce the coverage, you do want to keep things working properly.

Some options:
1/4 wave ground plane antenna. (easy to make yourself)
Small mag mount with a 1/4 wave
Small mag mount with a rubber duckie antenna

I didn't know that about the rubber ducks on a mobile.

I could go to a 1/4 wave, but I'd still be far over the power necessary. I can hit 3 repeaters in adjacent counties with a VHF handheld from my ranch. I also check into a VHF simplex net that covers about 4 counties from my place on my base station.

Since some transmissions can get a bit candid, not bad, just personal, I'd like to limit range as much as I can.


Delta

 

[kayn1n32008]

That might work, but I'd have to get a PL-259 90 degree.






I didn't know that about the rubber ducks on a mobile.

I could go to a 1/4 wave, but I'd still be far over the power necessary. I can hit 3 repeaters in adjacent counties with a VHF handheld from my ranch. I also check into a VHF simplex net that covers about 4 counties from my place on my base station.

Since some transmissions can get a bit candid, not bad, just personal, I'd like to limit range as much as I can.


Delta

Most hand held antennas don't give a portable a 1:1SWR match. I know because I did a bunch of tests with some hand held antennas for Jerry at CSI.

If you want to really reduce range, take your mobile to a shop that has the correct software and test gear, and have them set the low power setting to 5 watts, then program your channels for low power.

A cheap and easy attenuator at GMRS frequencies, is about 10 metres of RG-58. At 460MHz, that should attenuate your 10w carrier by at least 3dB(5w out the other end) if you need less power, at another 10 metres. Use an NMO 1/4wave with a base station adaptor(0 gain) and you should be good to go.

This is the ONLY time is will say this about 400MHz feed lines: Skip the high quality coax, use something cheap and lossy like RG-58.

It is really lossy at 460MHz. No, you will not hear as well, but if you are using a portable from inside a building, you should be just fine.

UHF is more about LOS than power. I think you will find, if you are using an outside antenna, that even with a couple of watts into the feedline, you will still overshoot your ranch quite significantly. Especially if the office is on high ground.

 

[pinballwiz86]

Since some transmissions can get a bit candid, not bad, just personal, I'd like to limit range as much as I can.

Get yourself a dummy load instead of an antenna. Go ahead and google dummy load to find something you like and is rated for the 10 watt power level and length of your transmissions. Connect your equipment to a dummy load, and you will limit your range to just your property!

 

[kayn1n32008]

I'm looking for an antenna like this, except in 460MHZ range.

MFJ Enterprises Inc.

Yes, I tried google, they don't seem to carry one.

Delta

Back in the day TopCon had a UHF rubber duck antenna that could be vertical or bent over on a hinge at 90 degrees they used for their Hiper head RTK rover. I think Larsen may sell a specialty antenna that does what you are looking for. Like mmkenna said, it is not a good idea though. Transmitting high power RF that close to both you and the radio is not a good idea.

 

[Seven-Delta-FortyOne]

Most hand held antennas don't give a portable a 1:1SWR match. I know because I did a bunch of tests with some hand held antennas for Jerry at CSI.

If you want to really reduce range, take your mobile to a shop that has the correct software and test gear, and have them set the low power setting to 5 watts, then program your channels for low power.

A cheap and easy attenuator at GMRS frequencies, is about 10 metres of RG-58. At 460MHz, that should attenuate your 10w carrier by at least 3dB(5w out the other end) if you need less power, at another 10 metres. Use an NMO 1/4wave with a base station adaptor(0 gain) and you should be good to go.

This is the ONLY time is will say this about 400MHz feed lines: Skip the high quality coax, use something cheap and lossy like RG-58.

It is really lossy at 460MHz. No, you will not hear as well, but if you are using a portable from inside a building, you should be just fine.

UHF is more about LOS than power. I think you will find, if you are using an outside antenna, that even with a couple of watts into the feedline, you will still overshoot your ranch quite significantly. Especially if the office is on high ground.

Thank you to all who responded.

I'm rethinking this whole set-up now.

I really appreciate all the help I get here. It always amazes me the knowledge that you folks have, those of you who work in the industry.


Delta

 

[Firebuff880]

Thank you to all who responded.

I'm rethinking this whole set-up now.

I really appreciate all the help I get here. It always amazes me the knowledge that you folks have, those of you who work in the industry.


Delta

https://www.tessco.com/products/displayProductInfo.do?sku=17174

 

[mmckenna]

https://www.tessco.com/products/displayProductInfo.do?sku=17174

Yeah, but then back to the higher SWR, RF being radiated places you don't want it, etc.

If you really want to dull down the performance, get one of the "phantom" style antennas. mount it with a small ground plane on the end of a long piece of RG-58, as kayn1n32008 suggested.