icom 7300 as a reciver

[Detroit47]

I would like to pair an Icom 7300 with a 32-v2. Any thought on how to mute the 7300?

Johnathan N8QPC

[K8DI]

I would like to pair an Icom 7300 with a 32-v2. Any thought on how to mute the 7300?

I don’t know the details of the 7300. A look at the manual for the external connections shows it to be very similar to the 7200, which I own.

With the 7200, I found there was no way to actually mute it. Stacked coaxial relays supposedly good for 100dB of isolation were still not enough to keep the AGC from being obliterated to the point that I’d miss the beginning of return calls as the gain came back up. 

My eventual solution was to write CAT codes to shift the receive frequency by 10kHz and back as part of the T/R switching setup for the home brew AM transmitter I paired it with.  Clunky and weird, but it solved the problem. 

Ed

[WB4AM]

Hello,

Unless I am missing something and lots of times I have, couldn't the 7300 be put into transmit with the external coax relay external contacts
(A Coax Relay with the external contacts that are mounted on the coaxial relay frame/body) during the transmit of the 32v2?

The RF Power of the 7300 of course would need to be turned off during its transmit mode.   This would certainly mute the 7300's receiver.

Please excuse my ignorance if I am not thinking clearly on the matter.

I have done this several times with other transceivers even an Anan SDR.

[KQ6F]

I agree with WB4AM.  You can turn down the RF output of the 7300 and use the SEND output to key your amp by going to XMIT.  I don't have a 7300 but a peek at the manual tells me the SEND voltage level is 16v.  That may or may not be enough to key your amp.  If not, then use a relay.

[Pete, WA2CWA]

Why not use a Dow-key or equivalent antenna relay with external relay contacts and just run the hot speaker lead through the external relay contacts. Key the transmitter, Dow-key energizes and opens the external relay contact breaking the speaker lead. No software tweaks, no internal diddling, simple. If you're creative and have additional relay contacts, you could wire in and ground the receiver input when keying the transmitter. You can even use a separate external relay to do the same thing.

If you like to do things manually, you can use one of these below.

How did we survive back in the "good old days"? No Internet, No Facebook, No Elmer's (just very old and nasty operators) 

[WD5JKO]

Besides using relay switching, use the 7300 as the exciter for the 32V, with a dummy load, or pi attenuator, feeding a toroidal transformer to isolate, and then plugged into a crystal socket.
Now you are capable of transceiver operation with precision frequency capability for both Tx and Rx.

The 32V VFO may be frequency multiplied on the upper bands. Maybe the 7300 can operate split?

Jim
Wd5JKO

[K8DI]

Why not use a Dow-key or equivalent antenna relay with external relay contacts and just run the hot speaker lead through the external relay contacts. Key the transmitter, Dow-key energizes and opens the external relay contact breaking the speaker lead. No software tweaks, no internal diddling, simple. If you're creative and have additional relay contacts, you could wire in and ground the receiver input when keying the transmitter. You can even use a separate external relay to do the same thing.

My experience with doing both these things at the same time, was that disconnecting the speaker did nothing to improve overloading the front end, and even with two coaxial relays (the second one connecting the receiver to a shorted N connector) AND another regular relay in a metal box that was inline with the antenna cable to the receiver that shorted the cable a foot from the receiver, the input was still overloaded to the point the AGC recovery time (on fast of course) was too long.  Cable was all LMR240, connectors all N except the actual radio connection. 

Using the iCom as an exciter "solves the problem" but may not be what the OP wants to do. For me, I wanted to use the crystals I had collected and the oscillator I built, at least to prove to myself that it worked...

What may work best, and I would try if I went back to it, is instead of shorting the receiver input with the second coax relay, connect that port to a dummy load and put the rig into transmit.  iCom has no way to turn the RF output down to zero -- about 5 watts is the lower limit -- so some load is necessary. Checking for any oddball intermodulation from the transmitter and the transceiver both generating RF at the same time would be necessary.  I haven't gone back to it because that transmitter is now paired with a boat anchor receiver with a proper mute input that cuts off the 1st RF amp tube.

Topic swerve --  I use a Yaesu radio as an exciter for my RCA transmitter.  Yaesu implements a "TX request" line to allow for tuning a linear amp with a  CW signal while in other modes. So while in AM, that line will put the unit into CW TX, with an independent power level control.  Very convenient!

Ed

[KD1SH]

   I use a method similar to what Pete suggests; all done automatically with relays. The MIC's PTT closes the coaxial relay, but doesn't key the transmitter just yet. The auxiliary contacts on the coaxial relay actuate a DPDT relay which provides additional isolation by using one set of contacts to open the receive line again and also ground it. The second set of contacts on the DPDT relay actuates two more relays, one of which shuts down my computer speakers, while the other enables the PTT, insuring that there's no way the transmitter can key up until all the correct conditions are met. Finally, and this is optional but adds still additional protection to the receiver, I've got an Array Solutions receiver overload protector (https://www.arraysolutions.com/surge-and-rf-protection/as-rxfep) in line with the receiver.
   I'm using this setup with an SDRPLAY unit, but I see no reason that it wouldn't work with a 7300 (I've got one; maybe I'll try it), other than AGC recovery, which hasn't proven to be a problem with the SDRPLAY.
   Sure, it's a little involved - maybe almost "Rube Goldberg" to some - but it's safe for the receiver and versatile enough to be used with almost any receiver. I'd originally considered adding a sequencer to insure that everything happens in the proper order, but the inherent delay in the relays is sufficient.

[WA1LGQ]

I mute my 7300 by yes, transmitting, but set it up for split operation where it "transmits" on a freq out of the ham bands where it won't actually transmit.
Larry

[kb3ouk]

I use a icom 718 at the moment as a receiver for my 814 rig and on the 718 in their initial set mode (hold set while turning the rig on) you can enable/ disable transmit and receive by mode. I just went in and disabled am tx, then use a contact closure from the homebrew rig to the back panel ptt connection on the 718 to key it. Works just as good as if you were using the 718 as a transceiver by itself.

[KD1SH]

Now that's a sharp idea, Larry - and you don't even have to turn down the TX power, since it won't transmit anyway. Actually, I didn't know that the 7300 would let you program it for frequencies outside the ham bands. When I try using my 7300 as a receiver on 6 meters, I'll give your idea a try.
See you Saturday at the Museum!

I mute my 7300 by yes, transmitting, but set it up for split operation where it "transmits" on a freq out of the ham bands where it won't actually transmit.
Larry

[WA1LGQ]

Oh, and yes when set up this way, the keying output on the back still works even though it does not actually transmit. Beware, like someone said, its 16 volts or something max, so you could blow it up if you try to key an unmodified SB220 for example that uses a fairly high relay keying voltage.

[K8DI]

I mute my 7300 by yes, transmitting, but set it up for split operation where it "transmits" on a freq out of the ham bands where it won't actually transmit.
Larry

Brilliant!  I wish I’d thought of that before I wrote all the code to query the radio for the frequency, parse it, change it, and reset it at each PTT activation!

Ed

[Detroit47]

Thanks for all the reply. Larry your idea is brilliant totally KISS.

Johnathan N8QPC