[MRCA] RF-1110B getting closer

[B. Smith]

The problem with antenna switching  during high power ops is obtaining 
proper sequence and isolation. Improper timing of the relay will result 
in turning a typical DOW relay into a paper weight. In addition you run 
the risk of blowing out a front end of a receiver. These problems are 
very prone during constant carrier ops such as RTTY and CW.   You will 
be amazed at how much RF is on the Antenna Terminal of a typical relay 
during transmit. There have been scores of articles and circuits 
published on the subject.  Makes you think about the gain vs the risk, 3 
or 4 db is not even a "S" unit.
Z

On 11/30/2021 5:10 PM, W2HX wrote:
>
> Ray, I think you want J11-6 on the exciter. Manual calls this “SYSTEM 
> KEYLINE” and I believe it. Looking at the manual it is asserted low 
> meaning /system-keyline and is the collector of an output transistor. 
> So I would assume a pullup resistor and +5V. maybe an opto-isolator 
> and then your TR relay.  Keying the TR relay off the exciter (rather 
> than the amp) would seem a little safer to me. Any small delays of the 
> keyline that may occur through the amp would slow down the switchover. 
> The exciter, being the source of the keyline, should be the fastest 
> signal.
>
> 73 Eugene W2HX
>
> Subscribe to my Youtube Channel: 
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> *From:* mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> 
> *On Behalf Of *W2HX
> *Sent:* Tuesday, November 30, 2021 4:41 PM
> *To:* HarrisRadio at groups.io; mrca at mailman.qth.net
> *Subject:* Re: [MRCA] RF-1110B getting closer
>
> I would not use any interlock signals. I would use only PTT or CW Key 
> (or OR them together). I will check the 1310 manual, but there may be 
> a /KEYLINE signal that is already OR’d . Let me look and I’ll get back 
> to you
>
> 73 Eugene W2HX
>
> Subscribe to my Youtube Channel: 
> https://www.youtube.com/c/w2hx-channel/videos 
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>
> *From:* HarrisRadio at groups.io <mailto:HarrisRadio at groups.io> 
> <HarrisRadio at groups.io <mailto:HarrisRadio at groups.io>> *On Behalf Of 
> *Ray Fantini
> *Sent:* Tuesday, November 30, 2021 4:34 PM
> *To:* HarrisRadio at groups.io <mailto:HarrisRadio at groups.io>; 
> mrca at mailman.qth.net <mailto:mrca at mailman.qth.net>
> *Subject:* [HarrisRadio] RF-1110B getting closer
>
> Every step forward revels three additional steps. Ok, so now I know 
> way more about key line interlocks and PTT returns and the like and 
> have my RF-1110B and RF-1310 working together along with making power 
> on amplifiers 1 and 2 and one driver, just need to now resolve blown 
> FET in “B” driver and one of the MRF-150 devices that’s just decided 
> to short gate to source but that’s the little issues because I am 
> content to just live with one side working for now.
>
> The new problem now is having to build some form of T/R switching so I 
> can get the radio on the air along with the companion receiver.
>
> Figure I can use a Dow Key Relay for the T/R switch and was looking at 
> the two signals available on J-8 the accessory port. First is the PTT 
> Key Line that’s jumped (B-D) and appears to be held high and goes low 
> when keyed, then there is a exciter interlock that’s jumped(I-J) on 
> the same plug that’s low and goes high when the transmitter is keyed. 
> What would be better to use? The exciter interlock looks like maybe 
> its generated after the PTT line and maybe that’s best? Or are they 
> both available at the same time?
>
> Going to assume that the RF-110 tube amplifiers are just about the 
> same deal for keying and control so wonder what everyone else is using 
> for T/R switching at the systems.
>
> And last but not least anyone done a group buy or have a good source 
> for the power FETs
>
> Ray F/KA3EKH
>
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