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Author Topic: TS 590SG Sub Reciever  (Read 937 times)
KB7FSC
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Posts: 96




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« on: November 27, 2017, 07:03:15 AM »

I've done some research on this, and I'd like to run this by you folks and see if I'm on the right page.

I currently have a TS 590SG connected to an SDR-Play RSP1a pan adapter via the DRV port.  What I'd like to do is split the DRV port so I can connect the SDR-Play and a TS 480 at the same time.  My thought is the 480 will act as a nice sub-receiver that is easy to operate and I can continue to use the SDR-Play as my pan adapter.  I've found other hams with the DRV port either driving a pan adapter or separate receiver, but not both at the same time.

My research is turning up some issues with splitting signals.  In addition to the 3 db+ split loss, there is also an impedance balancing issue.  Also, there are issues with pass frequencies of various splitters.  What I'm considering is using a DX engineering MB-2 Passive splitter.  It has a frequency range of 500 khz to 2.4 Ghz, so it should work great for HF frequencies.  The MB-2 is fitted with F type female connectors and is designed around 75 ohm impedance.  I was considering using RG-6 with F type male connectors, and using adapters at the DRV port, SDR-Play and TS 480.

Here are my questions:
1 - Will the 75 ohm impedance be a major problem for receivers?
2 - Is there a better way of splitting the signal?
3 - Is there a better way of facilitating this arrangement?

Thanks for taking the time to read this, and any expertise that is shared!

Wane - KB7FSC



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AC7CW
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Posts: 1002




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« Reply #1 on: November 27, 2017, 08:53:46 AM »

I was searching to find out exactly just what the DRV port is, came across another thread on eham that looks pretty informative and relevant http://www.eham.net/ehamforum/smf/index.php?topic=100599.0

Max
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Novice 1958, 20WPM Extra now... (and get off my lawn)
KB7FSC
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Posts: 96




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« Reply #2 on: November 27, 2017, 09:49:07 AM »

Hi Max,

Thanks for the reply.  The DRV port in a 590SG can be configured to output a small signal to drive other devices, or configured as an antenna tap for connecting an additional receiver.  There is a relay in the 590SG that activates when transmitting to disconnect the transmit path from the DRV port and prevent damage to the connected receiver.  The use of the DRV port is set up in the menu.  The 590S did not have this function.  Sure is a slick and easy way to add a panadapter or another receiver to a 590SG!

Wane

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AC7CW
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Posts: 1002




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« Reply #3 on: November 27, 2017, 01:37:39 PM »

Thanks. Keep us updated on your project
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Novice 1958, 20WPM Extra now... (and get off my lawn)
K6BRN
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Posts: 488




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« Reply #4 on: November 27, 2017, 08:03:39 PM »

Wane(KB7FSC):

Receiver impedance matching is not very critical in this case and you can use a simple "T" splitter to feed both the RSP-1 and TS-480 receivers with a nearly imperceptible loss of signal strength.  Note that the DRV output on the TS-590SG is an RCA jack - its not impedance controlled, anyway.

So you can use a 1:2 RCA splitter cable to an RCA to PL-259 adapter that feeds into the TS-480 antenna port, and an RCA to SMA adapter going into the RSP-1 antenna port.  Any similar arrangement will work.

BUT THERE ARE SIGNIFICANT PROBLEMS/DANGERS IN DOING THIS

1. The TS-480 is a TRANSCEIVER and can easily transmit INTO the TS-590SG and RSP-1 receiver antenna ports, destroying them.  It just takes a moment and a small amount of TX power for this damage to happen.  And it can be caused by you making a simple mistake, a turn-on transient, etc.  Even if the transceiver has a software TX lockout, this problem may occur.

For that reason, I strongly recommend you use a dedicated receiver rather than the TS-480 TRANSceiver to connect to the TS-590SG DRV (RX out) port.  AVOID POTENTIAL DAMAGE! Good choices include another SDRplay device, an R1000, R5000 or R75... etc.  (There are many good choices at all levels of performance and cost - try the used market and ebay in particular - they tend to protect the buyer, especially if you use PayPal.)

2.  The RSP-1 and likely any other receiver/transceiver you connect generates undesired internal spurs on RX that they actually output to the antenna port.  So each receiver will "see" the other receiver's spurs.  This is NOT a show stopper by any means, but when it happens and you notice a phantom signal that moves across the RSP-1 waterfall as you tune the other receiver, don't be surprised.  A matched splitter will NOT prevent this problem.  An active 1:2-port buffer would be needed at HF for reasonable isolation - too much trouble to solve a small issue.

3.  The TS-590SG DRV port, when configured as an RX out port, may accept the signal from the antenna AFTER the bandpass filters.  So you may not receive well when the TS-590SG is set to one band and the 2nd receiver to another.  Many transceiver RX out ports work this way, and some even pass the signal on after the main radio's RF amp and attenuators - which can be an advantage, if you have a 2nd receiver that can take advantage of additional filtering and a good preamp/attenuator - like the RSP-1.

I have both the SDRplay RSP-1 and an Icom R75 receiver connected to my FDTX-3000 in a similar manner.  But I have to point out that the RSP-1, by itself, is a fair 2nd receiver, and can maintain the waterfall display at the same time as you "browse the band".   Just "point and click" on the waterfall and select the right mode.  HDSDR software for the RSP-1 even has pretty good digital noise reduction built-in.

Good Luck - but also make your own - avoid connecting a transmitter to a receiver input.  Sooner or later someting bad is likely to happen.

Best Regards,

Brian - K6BRN
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G4AON
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Posts: 1027




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« Reply #5 on: November 27, 2017, 10:56:36 PM »

Wane, there is no need to buy a passive splitter as they are easy and cheap to make. However, you will have a loss through the splitter. I guess you could make a basic “distribution amplifier”, but it’s starting to get too involved for the benefit.

I sometimes use an external splitter with my Elecraft K3, the circuit and measured results are at:
http://www.qsl.net/g4aon/elecraft_mods/

73 Dave
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KU3X
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Posts: 431




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« Reply #6 on: November 28, 2017, 12:20:03 PM »

Whether your receiver sees 50 ohms, 25 ohms or 100 ohms.....you will not see any difference in the receive signal.
You already know that splitting the signal will decrease your signal by 3 db. Big deal ! So the guy you are listening to is S 6. Now he's probably S 5-1/2.
Now if the guy is in the noise and you can just about make him out, now the 3 db becomes an issue.

Here is my TS590SG with the TS 480SAT as a sub receiver. I kind of explain how to set the system up.

https://www.youtube.com/watch?v=StokNdN3m5Q&t=8s

Don't waste your money on anything external for setting up a sub with the 590SG, this does it all and it works great.


Barry

\www.ku3x.net
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KB7FSC
Member

Posts: 96




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« Reply #7 on: November 28, 2017, 07:14:33 PM »

Thanks for the thoughtful reply Brian.  I'm glad I posted this question on the forum.  As you mentioned, I did lock out the transmission function of the 480 in the menu system thinking my transceiver had now become a receiver.   I hadn't considered the possibility of transients from my 480.  On that point, aside from a glitch during power up, what else might create these sorts of spikes?

I am impressed with the RSP1a receiver and software.  It hears and filters much better than my previous SDR dongle, and the frequency stability is excellent.  A couple of reasons I'd prefer to use the 480 for a sub receiver is for working split and perhaps in contests.  It is also real time with the audio, and quick to tune and operate.  With the RSP1a, I do notice probably a 1/2 second lag by the time it processes the audio.  I also have to unlink it in the software so I can tune it separate from the 590.  These are certainly not huge issues, and if I had to choose, I would not give away the pan adapter functionality. 

Soooo, at this point, I'm getting cold feet thinking about spiking my new 590sg and thinking I might just use the RSP1a as my sub receiver.  I'm curious how long Barry - KU3X has linked in the 480 as a sub receiver for his 590sg?

I also appreciate the input from all the other posters.  It doesn't sound like the impedance mismatch will be a major obstacle either for the receiver. 

Thanks again for the advice and information.  It is appreciated!

Wane - KB7FSC
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K6BRN
Member

Posts: 488




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« Reply #8 on: November 29, 2017, 04:55:55 PM »

Hi Wane:

Another condition that could cause a firmware/microprocessor based rig to transmit when the TX/RX port was "locked" by a menu setting into RX only is an upset in the rig's microprocessor, most often caused by RF in the shack.  When that happens, anything goes.

Before I finished installing the ground system and RF feedline chokes in my station, I would have weekly upsets in the FTDX-3000, mostly when running about 500W on SSB, from RF feeding back into the rig.  Symptoms varied a lot, but often it would lock in TX mode, sometimes the front panel would lock, etc.  At that time I was using an FTDX-1200 I had as a 2nd receiver, feeding into the RX only port on the FTDX-3000 with TX "locked out".  It would also occasionally lock up too, in a variety bizarre states, and seeing that the FTDX-3000 would sometimes lock in TX mode, I disconnected it pretty early on (better safe than sorry - and an expensive repair).  So my receiver never blew up.

I switched to an SDRplay RSP-1 as a combo 2nd receiver and panadapter, and later added an Icom R75 so that I have both a dedicated panadapter and search receiver.  The FTDX-3000 has both a 9 MHz IF output and an RX only output, which makes this easy to do.  However, I often find myself pointing and clicking on the SDRplay waterfall simply to check out an interesting signal and it works well as a 2nd receiver, too.  Audio quality is mainly determined by the quality of your computer speakers, and in my case, is pretty good.

Brian - K6BRN


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