Page 1 of 1

Your MFJ-1708B-T/R Switch Experiences

Posted: Mon Jan 14, 2019 6:01 pm
by Ruben_NB4R
I have an new RSP1A and an MFJ-1708B-SDR. I have read all I can find in this forum pertaining to this matched pair, but am not seeing the information I'm needing. I would like to hear from anyone that is using the RSP1A with the MFJ-1708B-SDR without having made any other modifications. I've read about diode protection and cascading relays off the mic PTT contacts. The MFJ-1708 is supposed to ground the input to the RSP1A when the switch is in transmit mode.

I plan on using the pair on a Yaesu FT1000-MP and an Ameritron AL80-b amp. I will be inserting the switch between the transceiver and the amp. I do like the idea of the cascading relay idea and just might implement that idea. I also read where some have gained receiver protection by putting the receiver in an aluminium box. I don't know why the SDRPlay don't make this standard practice if it is so needed. I am open to suggestions and ideas, but I would really like to hear what your experiences are if you Use the RSP1A/MFJ1708 pair without mods. Thank you very much!
73
Ruben_NB4R

Re: Your MFJ-1708B-T/R Switch Experiences

Posted: Sun Jan 20, 2019 1:23 pm
by JohnAE5X
It is not needed in many applications, such as SWLing, ADS-B monitoring, etc. For those/us users, an aluminum box would be an added and unnecessary expense. I'm happy to have the option of buying just as much product as I need and no more.

John AE5X
_______________________________________

"I also read where some have gained receiver protection by putting the receiver in an aluminum box. I don't know why the SDRPlay don't make this standard practice if it is so needed."

Re: Your MFJ-1708B-T/R Switch Experiences

Posted: Mon Jan 21, 2019 5:30 pm
by ON5HB
First of all the inside of the RSP1A is sprayed with a metal paint as many reviews have pointed out, also they state it's effective.

I have ordered the MFJ1708B myself, but currently I'm running the Icom 7300 with an Acom 1010 pretty close to it, it's not disconnected from my Inverted-L 160m antenna (at less then 2m distance 90 degrees angled) and only protected with a NoElec 125MHz upconverter.

Both have extra protection, yes the RSP1A does also.

I can load my G5RV up to 1 KWpeak and nothing happens to the RSP1A except being overloaded in the waterfall.

The MFJ effectively shortens the SDR port when in TX or being powerless as you can see in the schematics.
It's also TX sensitive, so even if you don't connect PTT it will still switch.

There is no need for a metalbox as it's protected with paint at the inside and it will not break when you TX.

Do not worry, nothing will happen to the RSP1A.
I abuse the hell out of the 3 I have, so far nothing happened and my websdr users love it when they see me making contacts, at first it scares the hell out of them thinking my websdr is falling apart :lol:

Do not do what I do on purpose! But they do not break that easy.

Re: Your MFJ-1708B-T/R Switch Experiences

Posted: Mon Jan 21, 2019 8:55 pm
by vk3alb
Ruben_NB4R wrote: I don't know why the SDRPlay don't make this standard practice if it is so needed.
Ruben_NB4R


The RSP2pro comes in a metal box but also comes at a price. As has already been mentioned not everyone needs such heavy shielding.

Re: Your MFJ-1708B-T/R Switch Experiences

Posted: Sun Mar 17, 2019 12:13 pm
by SV1RXI
Hi team. I also read some posts about the mfj1708b sdr s. I have now the 891 and just 2 days ago i buy the rsp1a. The first version of the mfj i read many complains about high swr. Also see the mfj is one way road. There is also one dx Engineering product RTR-2 but is very expensive and i don't know if it needs others equipment to work for. Also maybe i use the 7300 with the mfj and share the same antenna, bust most i use the yaesu 891. Any worries or other thing to look and some of you experienced with 1708b sdr s.? Thanks