Re: G0MRF downconverter

Colin Ranson

Hi Paul,


I really fail to see where you are coming from. I never suggested for one moment that the IC-706MK2G could transmit and receive at the same time.  All I want is full transceive, marrying up the uplink IF and the downlink IF as being on the same frequency on the radio, obviously the RIT will almost certainly have to be used to some extent.

The signal strength into the transponder can be monitored on the WEB SDR from Goonhilly..... or if that goes down I have a second  dish with stable LNB I can feed into a dongle at 739MHz.   

Just out of interest on the uplink I use an SG Labs transverter into an SG Labs 20w amp throttled back to 15w. Uplink antenna is a so called ‘professional Super Cannon’ - a 16 turn helix made for the drone market with my modification of an arrow shaped tab inserted at the first quarter turn for the amp to ‘see’ a proper 50ohm.  

The amplifier and 25MHz reference sit on the windowsill the other side of the shack with the helix on the other side of the wall.  As soon as I hopefully get some success with a new 25.788461++++ MHz reference using the Si clock chip I will let everyone know. I am not one hell of a know-all, far from it, I will have to get my good friend Martin Waller to program the ‘NANO’ or even a ‘MICRO’....that’s beyond my 70 year old brain these days.


I’ve just thought, if I do that I will need a bias tee ! 12v for the LNB presently derived from the MRF downconverter.


Best regards to all,


Colin de G8LBS, Ipswich.



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From: Paul Randall G3NJV
Sent: 06 September 2020 21:57
Subject: Re: [UKMicrowaves] G0MRF downconverter


The IC706 cannot transmit and receive at the same time. You need an IC-821 or IC-910 or another "satellite" rig for that. "Full duplex mandatory" is not about having a full duplex communication circuit, it is specified because you are accessing a linear transponder and MUST monitor your uplink in real time to ensure you are not too "hot". You can check your uplink using the web SDR at Goonhilly and use a traditional half duplex "press to talk" rig for your communication circuit - easy.


Satellite DID virtually replace undersea cables on thick routes - e.g. carriers put up to increase capacity at Christmas to USA/Canada/Australia had thousands of telephone circuits - an order of magnitude increase over coaxial cables. Then fibre happened.


Hearing noises coming back at you while you are talking makes people hesitate and pause their speech, it is after all, POLITE to do so; upbringing, social skill, we learn to do this to participate in normal conversations. A common problem on HF marine circuits that pre-dated satellite, so possibly not so much an issue of delay.  I have recordings of conversations on HF completely halted by "politeness" even though the "communication speech circuits" are fully operational - sometimes the "operator" had to break in to get things moving again. Mastering this issue was, and still is today, a MUST for professionals, Coastguard, Air traffic control, etc - it is largely a case of becoming a bit boorish and completing your sentence no matter what you hear - ears off mouth on. Yes, you might have full duplex, but to communicate effectively you may (mentally) need to use it like half duplex.

Thats my 2p worth

Cheers Paul


From: <> on behalf of PAUL NICKALLS via <paulnick@...>
Sent: 06 September 2020 19:47
To: <>
Subject: Re: [UKMicrowaves] G0MRF downconverter


The delay is why the telephone system will not use 2 satellite links on a telephony circuit.  It was thought that satellites would replace undersea cables. However ......

Paul G8AQA

On 06/09/2020 15:39, Andy G4JNT wrote:

Good ooint Colin, forgotton that as I don't use SSB on the satellite.   John, haedphones doesn't solve this impossibility many have of being able to talk properly when your own voice is delayed by even a 100ms.    I got really badly tied up on a Zoom meet recently when one participant was relaying the received audio, so everyone  else got their voice back a few 100ms after it was spoken.


Only ever used voice on QO100 a handful of times when it first started and it was impossible to even say one word without stuttering when my own voice came back after a delay.   So I had to turn the volume down on Tx anyway, in the absence of a mute facility.


Which makes a complete mockery of the "mandatory full duplex" guideline






On Sun, 6 Sep 2020 at 15:20, John Fell <john.g0api@...> wrote:

Headphones ?





On Sun, 6 Sep 2020 at 14:48, Colin Ranson <g8lbs@...> wrote:

Andy, I find listening to my downlink audio makes me stutter, I just look at my waterfall.  I turn off the extension speaker on the FT460 with a relay coupled to the IC-706 PTT.


Cup of tea time.


Colin de G8LBS.


Sent from Mail for Windows 10


From: Andy G4JNT
Sent: 06 September 2020 12:48
To: UK Microwaves
Subject: Re: [UKMicrowaves] G0MRF downconverter


Just a comment

"Full Duplex, mandatory"

Whaaaaatttt ?

Who listens to their downlink - it generates howl-round if nothing else.


All you have to be able to do is listen on your Rx frequency.   And on satellites, that means your downlink - it doesn't have to be simultaneous.






On Sun, 6 Sep 2020 at 12:34, Mike Willis <willis.mj@...> wrote:

Can the IC706 dull full duplex? Not sure it can so you can't really use it with QO100 without something to provide the duplex, which is after all, a mandatory requirement. As you then need two radios anyway so it's probably better their IFs are in different bands. An SDR receiver is the simple choice and it doesn't need a downconverter, but something that does satellite modes, like a TS2000 or FT726/736 would be good.
Mike G0MJW




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