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OT: Advice re: blocking RF from rx-only antenna

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David Herring-3

OT: Advice re: blocking RF from rx-only antenna

Hi Everyone,

Yes, this is off-topic a bit, but I know there are some of you here who will be able to get me going in the right direction.

I have a PixelSatRadio RF Pro 1A receive-only moebius loop antenna. It is being used with a Kenwood TS-440S that does not have the provisions for a receive antenna like the K3 does. In order to make sure one doesn't fry the antenna's pre-amp, I need a fool-proof way to ensure that no one ever accidentally sends RF down the coax to that antenna.

I have thought about maybe some kind of a PTT enabled antenna switch.

I have thought about some kind black box with a circuit one could build that would act as a gatekeeper to allow RF in from the antenna but block any going out.

I have searched the 'net and have not yet found anything along those lines that I could implement.

So my question to you is, can anyone here recommend such a switch or such a black box circuit? Or maybe propose something else that I'm not even thinking of? Any ideas, suggestions, recommendations?

I need this to be on-the-cheap and I'm not opposed to homebrewing something here, though I only have modest-at-best skills in homebrewing.

Many many thanks,

Dave, AH6TD

I now return this reflector to normal programming, already in progress. ;-)
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N8MSA

Re: OT: Advice re: blocking RF from rx-only antenna

I used, until recently, a ELAD transmit/receiver switch to protect the front end of my auxiliary receiver. I know that MFJ makes at one model as well (MFJ-1708), perhaps two. The ELAD switch isn't normally available in the US, but is frequently available used and can be ordered from Europe.

73,

Mike Alexander - N8MSA

[hidden email]

----- Original Message -----
From: "David Herring" <[hidden email]>
To: [hidden email]
Sent: Sunday, April 22, 2012 4:03:14 PM
Subject: [Elecraft] OT: Advice re: blocking RF from rx-only antenna

Hi Everyone,

Yes, this is off-topic a bit, but I know there are some of you here who will be able to get me going in the right direction.

I have a PixelSatRadio RF Pro 1A receive-only moebius loop antenna. It is being used with a Kenwood TS-440S that does not have the provisions for a receive antenna like the K3 does. In order to make sure one doesn't fry the antenna's pre-amp, I need a fool-proof way to ensure that no one ever accidentally sends RF down the coax to that antenna.

I have thought about maybe some kind of a PTT enabled antenna switch.

I have thought about some kind black box with a circuit one could build that would act as a gatekeeper to allow RF in from the antenna but block any going out.

I have searched the 'net and have not yet found anything along those lines that I could implement.

So my question to you is, can anyone here recommend such a switch or such a black box circuit? Or maybe propose something else that I'm not even thinking of? Any ideas, suggestions, recommendations?

I need this to be on-the-cheap and I'm not opposed to homebrewing something here, though I only have modest-at-best skills in homebrewing.

Many many thanks,

Dave, AH6TD

I now return this reflector to normal programming, already in progress. ;-)
______________________________________________________________
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David Herring-3

Re: OT: Advice re: blocking RF from rx-only antenna

Well, these certainly are compelling solutions, even though they are designed for separate transmitter and receiver, rather than separate transmit & receive antennas. I suppose one could just "use it backwards" so to speak, and it would work. More money than I'd hoped to pay, but not out of the question. Not a bad suggestion really, and I'm not sure how I missed these when I was searching.

Thing that I find myself wondering now is what would happen when the receive coax gets shorted to ground, as both these units do when in transmit mode...probably nothing, but that's a question for the antenna manufacturer.

Thanks, 73 & Aloha,

Dave, AH6TD

On Apr 22, 2012, at 10:11 AM, [hidden email] wrote:

> I used, until recently, a ELAD transmit/receiver switch to protect the front end of my auxiliary receiver. I know that MFJ makes at one model as well (MFJ-1708), perhaps two. The ELAD switch isn't normally available in the US, but is frequently available used and can be ordered from Europe.
>
> 73,
>
> Mike Alexander - N8MSA
>
> [hidden email]
>
> From: "David Herring" <[hidden email]>
> To: [hidden email]
> Sent: Sunday, April 22, 2012 4:03:14 PM
> Subject: [Elecraft] OT: Advice re: blocking RF from rx-only antenna
>
> Hi Everyone,
>
> Yes, this is off-topic a bit, but I know there are some of you here who will be able to get me going in the right direction.
>
> I have a PixelSatRadio RF Pro 1A receive-only moebius loop antenna. It is being used with a Kenwood TS-440S that does not have the provisions for a receive antenna like the K3 does. In order to make sure one doesn't fry the antenna's pre-amp, I need a fool-proof way to ensure that no one ever accidentally sends RF down the coax to that antenna.
>
> I have thought about maybe some kind of a PTT enabled antenna switch.
>
> I have thought about some kind black box with a circuit one could build that would act as a gatekeeper to allow RF in from the antenna but block any going out.
>
> I have searched the 'net and have not yet found anything along those lines that I could implement.
>
> So my question to you is, can anyone here recommend such a switch or such a black box circuit? Or maybe propose something else that I'm not even thinking of? Any ideas, suggestions, recommendations?
>
>
>
> I need this to be on-the-cheap and I'm not opposed to homebrewing something here, though I only have modest-at-best skills in homebrewing.
>
>
> Many many thanks,
>
> Dave, AH6TD
>
>
> I now return this reflector to normal programming, already in progress. ;-)
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: OT: Advice re: blocking RF from rx-only antenna

In reply to this post by David Herring-3

Dave,

That situation is dealt with routinely by VHF folks with mast mounted
preamps.
Using a coax relay to connect the amplifier to the antenna and a second
relay to connect the preamp to a 50 ohm load will usually provide
adequate isolation.

73,
Don W3FPR

On 4/22/2012 4:03 PM, David Herring wrote:

> Hi Everyone,
>
> Yes, this is off-topic a bit, but I know there are some of you here who will be able to get me going in the right direction.
>
> I have a PixelSatRadio RF Pro 1A receive-only moebius loop antenna. It is being used with a Kenwood TS-440S that does not have the provisions for a receive antenna like the K3 does. In order to make sure one doesn't fry the antenna's pre-amp, I need a fool-proof way to ensure that no one ever accidentally sends RF down the coax to that antenna.
>
> I have thought about maybe some kind of a PTT enabled antenna switch.
>
> I have thought about some kind black box with a circuit one could build that would act as a gatekeeper to allow RF in from the antenna but block any going out.
>
> I have searched the 'net and have not yet found anything along those lines that I could implement.
>
> So my question to you is, can anyone here recommend such a switch or such a black box circuit? Or maybe propose something else that I'm not even thinking of? Any ideas, suggestions, recommendations?
>
>
>
> I need this to be on-the-cheap and I'm not opposed to homebrewing something here, though I only have modest-at-best skills in homebrewing.
>
>
> Many many thanks,
>
> Dave, AH6TD
>
>
> I now return this reflector to normal programming, already in progress. ;-)
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>