Icom IC-7300 with AOR LA-400

[AOR-262]

Question for owners of the Icom IC-7300

My query is relating to connecting the AOR LA-400 Active Antenna (receive only antenna) to the Icom IC-7300.

Two questions ...

Does the Icom IC-7300 transmit in any way, that meaning anything at all if the unit does not have a microphone or any other device that would cause the IC-7300 to transmit?

If the 'TRANSMIT' button was accidentally pressed, would this cause any instant (or slow) damage to the AOR LA-400.

 

[ka3jjz]

If you were fooling around with the mic connections or perhaps on the insides, it is somewhat possible that you might trip the transmitter which would almost immediately fry the AOR. So why take the chance on an antenna that's about as overpriced as gold pressed latinum?? (Hi). A much better choice of loop - and a lot cheaper, too - would be a W6LVP loop with the T/R switch. That would disconnect the antenna if you transmitted by mistake. These loops have been almost universally praised as very good antennas, and the customer service is reportedly nothing short of exemplary. Use a different antenna for freqs above 30 Mhz. Here's the URL

W6LVP Amplified Receive-Only Magnetic Loop Antenna – With T/R Switch – W6LVP

Mike

 

[iMONITOR]

I'm surprised all transceivers do not have a way to inhibit the transmit mode, to prevent accidental or even intentional use by unlicensed users.

I've used high end amateur radio transceivers as receivers over the years due to their performance gains over typical receivers. I use an ICOM IC-7600 transceiver as a receiver only. Like you I keep the microphone disconnected but there is a 'Transmit' button on the control panel. Also like you I used an active loop receive only antenna, the MFJ-1886 (highly recommended). Not sure if an internal automatic antenna tuner might transmit at some low level during the process.

 

[ka3jjz]

The older transceivers did - I can't see why these newer ones wouldn't as well.

I don't believe - I could be wrong - that the 1886 has a built in T/R switch. No reason you couldn't add one on as a separate unit, for sure. The LVP unit I gave for the link has it already installed.

Better safe than make an expensive mistake...Mike

 

[iMONITOR]

The older transceivers did - I can't see why these newer ones wouldn't as well.

I don't believe - I could be wrong - that the 1886 has a built in T/R switch. No reason you couldn't add one on as a separate unit, for sure. The LVP unit I gave for the link has it already installed.

Better safe than make an expensive mistake...Mike

You're pretty close Mike. MFJ also makes the MFJ-1886TR that has a built-in transmit/receive switch for $50 more than the MFJ-1886, so yes, it's probably worth it to pay a little more. Also some radios have more than one antenna connector. My IC-7600 actually has three. Two can transmit and receive and one is actually desgined only for receive.

MFJ-1886TR
MFJ Enterprises Inc.

 

[ka3jjz]

Ah OK very good - didn't know about the variation. I will add it to the wiki. Thanks for pointing that out. Mike

 

[iMONITOR]

Thank you Mike for all you do here on RR.

 

[AOR-262]

I'm surprised all transceivers do not have a way to inhibit the transmit mode, to prevent accidental or even intentional use by unlicensed users.

-- That's saying you can only buy/own/use a transceiver if you have an official radio ham licence. (you don't need a licence to buy a car, you must have a licence to drive a car but we know people do drive cars without licences, insurance etc)

 

[AOR-262]

Not sure if an internal automatic antenna tuner might transmit at some low level during the process.

That's interesting you say that. Do you know if the IC-7300 has an internal automatic antenna tuner?

 

[prcguy]

I second the W6LVP loop, fantastic performance for half the price of its competitors. On the Icom 7300, there is a mod to break the receive antenna path with two connectors on the back panel and a coax jumper. When the jumper is in the radio works as stock. With the jumper removed you can attach a receive only antenna and it will never see transmit power but the radio will still transmit through the stock antenna connector while using a separate receive only antenna.

I forget who offers the mod kit but you can get the parts on Ebay and do it yourself. I already bought a couple of internal coax jumpers with mating circuit board connectors and will drill holes in the rear of my 7300 to install good quality BNC connectors. The offered kit removes something on the rear panel and their connectors slide into a slot left over from whatever was removed. I would rather have the BNCs hard mounted to the rear panel.

 

[iMONITOR]

That's interesting you say that. Do you know if the IC-7300 has an internal automatic antenna tuner?

From what I've read, yes it does.

 

[prcguy]

Yes it does have an internal tuner but its not very wide range. It will handle a mismatch of 3:1 and maybe a little more but for anything worse the radio/tuner must be put into an "emergency mode" where the radio will only do 50 watts and then the tuner will work over a wider range.

Many people just get an LDG type tuner which will interface with the radio and work with the front panel tune button just like the internal tuner. I use an amplifier and a 1kW rated LDG tuner that is controlled by the radio and it works great.

From what I've read, yes it does.

 

[iMONITOR]

Do you know if it emits any RF output to the antenna jack when using the automatic tuner and not actually transmitting? The OP is concerned about buring out his external preamp.

 

[N9PBD]

Do you know if it emits any RF output to the antenna jack when using the automatic tuner and not actually transmitting? The OP is concerned about buring out his external preamp.

If the OP presses the "TUNE" button on his IC-7300, it will transmit a low power (10 watts) CW signal so it can measure the VSWR (to tune), which will most surely cook his expensive active antenna.

 

[nanZor]

Hum, I'm surprised that the 7300 doesn't have a tx-disable option in one of the menus. I know some of my Yaesu's did.

 

[AOR-262]

Do you know if it emits any RF output to the antenna jack when using the automatic tuner and not actually transmitting? The OP is concerned about buring out his external preamp.

Thanks iMONITOR for putting this conversation/thread back on track.

I'm not looking for advice on what receive-only antenna or any other antenna I can use with the IC-7300. The antenna is the AOR LA-400 (receive only) and I am trying to find out if the IC-7300 outputs any RF Signal at all in any way at any time for whatever reason without any user intervention i.e. does the 7300 send anything to the output connection on its own automatically for any reason or is it the 7300 will only send any RF Signal to the output connection if such a device such as a microphone or any other connected device that would cause the 7300 to transmit.

I am asking because I know of an instance where someone using the IC-7300 for receive only who's antenna is the AOR LA-400 ... their LA-400 has suddenly stopped working. I know nothing about transceivers and I believe (until proven wrong) that either the 'TRANSMIT' button has been accidentally pressed or a feature such as an Automatic Antenna Tuner has either instantly or slowly burnt out the circuitry of the LA-400.

 

[prcguy]

My 7300 is relegated to my travel trailer and I'll have to open it up to make measurements for power out in the tune mode when the radio power is dialed down to zero. Seems like I measured minimum power on the 7300 at one time and it was about 5w but I don't remember if that was at a setting of one or zero.

Thanks iMONITOR for putting this conversation/thread back on track.

I'm not looking for advice on what receive-only antenna or any other antenna I can use with the IC-7300. The antenna is the AOR LA-400 (receive only) and I am trying to find out if the IC-7300 outputs any RF Signal at all in any way at any time for whatever reason without any user intervention i.e. does the 7300 send anything to the output connection on its own automatically for any reason or is it the 7300 will only send any RF Signal to the output connection if such a device such as a microphone or any other connected device that would cause the 7300 to transmit.

I am asking because I know of an instance where someone using the IC-7300 for receive only who's antenna is the AOR LA-400 ... their LA-400 has suddenly stopped working. I know nothing about transceivers and I believe (until proven wrong) that either the 'TRANSMIT' button has been accidentally pressed or a feature such as an Automatic Antenna Tuner has either instantly or slowly burnt out the circuitry of the LA-400.

 

[N4GIX]

My 7300 is relegated to my travel trailer and I'll have to open it up to make measurements for power out in the tune mode when the radio power is dialed down to zero. Seems like I measured minimum power on the 7300 at one time and it was about 5w but I don't remember if that was at a setting of one or zero.

With the power turned down to "0", pressing the Transmit button in RTTY mode reads 0.9 watts on my digital meter.
Pressing the Tuner button when in RTTY mode reads 10.0 watts on my digital meter.

In "normal SSB" modes, Transmit button reads 0.0 watts because there's no modulation of course. The Tuner button however still generates 10.0 watts.

So, there's no front panel way to totally eliminate accidental RF from being sent out the antenna port.

 

[prcguy]

Only good solution is the aux receive antenna input mod and I found its made by INRAD and cost about $40. Here is one vendor: INRAD RX7300 Receive Only Input Modification Kits RX7300

With the power turned down to "0", pressing the Transmit button in RTTY mode reads 0.9 watts on my digital meter.
Pressing the Tuner button when in RTTY mode reads 10.0 watts on my digital meter.

In "normal SSB" modes, Transmit button reads 0.0 watts because there's no modulation of course. The Tuner button however still generates 10.0 watts.

So, there's no front panel way to totally eliminate accidental RF from being sent out the antenna port.

 

[N4GIX]

Only good solution is the aux receive antenna input mod and I found its made by INRAD and cost about $40. Here is one vendor: INRAD RX7300 Receive Only Input Modification Kits RX7300

I'd forgotten about that option being available. At the time I decided that it wouldn't be all that useful to me, given that it would remove the accy port I will need to connect to the PC and/or my SignaLink sound card for JT8, and other digital modes.

That would work to protect the receive only antenna, but I'd still opt to install a 100 watt dummy load on the main antenna port, just in case!