How to use a Flex 6k with Sdrplay rx switching

excalibrate · August 2023

Although I love my 6400M, sometimes I miss the SDR play for monitoring activity on bands and shortwave listening. So I want to hook that back up, on a separate antenna but have a TR switch to disconnect the sdrplay receive antenna while transmitting on the Flex. It was easy when I used it with my FTDX3000 since i just used the RF output on the Yaesu for the antenna on the sdrplay and it automatically disconnected it during TX. The flex doesn't have the option to feed the full spectrum out to another device. Wish it did.

So I understand I can use a TR switch controlled by on of the rca tx ports. Any recommendations for a simple and affordable TX/RX switch? Or any other ways to reduce the rf into the sdrplay while the im transmitting at legal limit on a different antenna?

Thanks

KG4FBY

Geoff AB6BT · August 2023

Here is one example relay on Amazon. The relay can be configured as either active high or active low:

HiLetgo 12V 1 Channel Relay Module With Optocoupler Isolation Support High or Low Level Trigger

Larry _ NY8T · August 2023

https://www.gigaparts.com/mfj-1708b-sdr-rf-sensing-switch-with-so-239.html?utm_term=sku-zmf-1708b-sdr&gclid=Cj0KCQjw6KunBhDxARIsAKFUGs-939LYiYEbLao29DzqsXI9On8xZiWY3zUuffQw1V6xShLzBZdl3lQaArXNEALw_wcB

https://www.gigaparts.com/mfj-mfj-1708b-sdrs-sdr-rf-sensing-t-r-switch-with-sma-female.html?utm_term=sku-zmf-1708b-sdrs&gclid=Cj0KCQjw6KunBhDxARIsAKFUGs_dPGlrsaa7N1_AY9tCkvpI44uHTu3BvPvXh-4yfaJTyp1Ub7FNayIaAiIjEALw_wcB

excalibrate · August 2023

I considered this but it has really poor reviews. Also, not sure its worth $140 to protect a $150 SDR.

Mr Radio · August 2023

Another option:

https://active-antenna.eu/

Mr Radio · August 2023

And one more:

https://www.eladit.shop/en-gb/Antenna-Switch-Box-ASW-2-p209053122

KD0RC · August 2023

Check out relay boards designed to be operated by Arduinos. One of those connected to TX1, 2 or 3 should do the trick. Simply opening the RX line to the RSP1A should be sufficient isolation. They are around $8.00 USD.

excalibrate · August 2023

https://community.flexradio.com/discussion/comment/20605264#Comment_20605264

This looks like an interesting option. Is the signal from tx 1, 2, 3 low enough (5v) to directly connect to this? Couldnt I just place in a box with a couple uhf connectors and a rca connected to tx1 to connect/disconnect the positive antenna lead?

excalibrate · August 2023

HMM, looks like it may be a bit more to it than that. I read tx1 shorts to ground if I understand the manual. But the accessory tx on pin 11 may have 5v on it. IDK, may be more than I want to experiment with. Will think about this.

Geoff AB6BT · August 2023

Pin 11: Accessory TX

This pin is a buffered PTT output identical to the three RCA connectors TX1, TX2, and TX3.

excalibrate · August 2023

OK, looks like it will work on tx1 but I have to power the relay board at the yellow plug on the right side. I have never played with the Arduinos before so trying to figure how to use the relay without connecting to Arduino. I think that might work. I havent found a manual on the relay yet.

excalibrate · August 2023

https://community.flexradio.com/discussion/comment/20605269#Comment_20605269

I like this option the best. I ordered a couple. They are cheap. Plus I got lots of 12v available in the shack. I will play around and see what works. Thanks for the idea Geoff.

KD0RC · August 2023

Here is a 4 channel relay board from Amazon (see link, below). These relays take 20 mA at 5V to actuate. The TX 1-3 lines go to ground when active. They will sink up to 140 mA at +40 VDC, so you can easily drive this relay board directly.

Amazon.com: SunFounder Lab 4 Relay Module 5V 4 Channels Relay Module Compatible with Arduino R3 1280 Arm PIC AVR STM32 : Electronics

Note that you need to check the RCA TX or ACC TX boxes. These settings are kept in your transmit profile. So be sure that whatever transmit profile you are using is active, or you run the risk of overloading your SDRPlay.

excalibrate · August 2023

Thanks. The diagram helps.

Thanks you all for the ideas.

Much appreciated

KD0RC · August 2023

Glad to help. We posted at the same time, so I didn't realize that you had the 12 V version. Just replace my reference to 5 V with 12 V.

excalibrate · August 2023

Im looking forward to this. I ordered some BNC bulkhead connectors and a small project box. Its like $20 worth of parts and some of my time. If it works for my purpose, it makes way more sense for a receive only antenna buffer. I will try to post back here after I build it and let everyone know how it works. For the next person wanting a simple solution like this.

Geoff AB6BT · August 2023

In addition to Len's drawing, I would suggest that you use both poles of the relay. Connect the common terminal to the input of the receiver and one pole to the antenna and the other pole to ground.

Just a bit more insurance...

excalibrate · August 2023

Not completely sure you you mean. Can you elaborate please?

Geoff AB6BT · August 2023

The relay hac 3 connections, NO, COM, NC.

Connect the Common to the receiver input, the Normally Closed to the antenna, (these connections are the same as in Len's drawing) and the Normally Open to ground. (the NO and NC contacts might be reversed depending on whether you configure the relay board active high or active low).

That way the receiver input is grounded and not floating when you transmit.

How to use a Flex 6k with Sdrplay rx switching

Best Answer

Answers

Leave a Comment

Categories