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Power Supply Requirements

iMONITOR

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#1
I'm posting in this forum for those who have considered using amateur ham radio transceivers for SWL only. Typically you read that these radios require a substantial 12VDC power supply that you might can't afford, or can't afford to run it, or just don't want a big power supply in your monitoring space. I'm one of those people that uses a transceiver for SWL. I use an ICOM IC-7600. If you were a ham and intend to use this you'd have to procure about a 25 amp power supply! However if you're using it for receiving only, the specs say it only requires ony 3.0A on standby and 3.5A at full audio. That might convince you to consider using a transceiver which often make superior receivers!

Note: In the U.S. you do not require a license of any kind to purchase or use a amateur-ham transceiver for receiving only. Never be tempted to transmit, in fact disconnect the microphone just to make sure!
 

spongella

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#2
Older transceivers, for example the Yaesu FT101 series and the Kenwood TS520 had built-in power supplies while others required separate outboard supplies. However, older transceivers like those above only received the ham bands. Over the years transceivers, in some cases had extended receive and would cover frequencies of interest to shortwave enthusiasts. You are correct that current draw on receive is much lower than when in transmit mode. I personally prefer having both a ham transceiver (since I'm a ham) and a separate shortwave receiver.
 
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#3
iMonitor - just a general rule of thumb being that for an external power supply you typically want to double the current draw, ie for your 7600 drawing 3.5A max, then a minimum of a 7A power supply is called for. Many will specify an intermittent and continuous draw specification, so be careful not to choose one too small.

A good choice for the older linear type of supply for just that radio would be an Astron 7A, or even better the 12A to handle any other preamps, filters etc that you may add on. Both may also accept any temporary power-on surge by doubling the rating of your receiver current draw.

Not connecting a mic or key to prevent transmitting is also a good idea of course - but fat-fingering a transmit function button to an open antenna port, or one that has rx-only components (like a Par EF-SW rx-only transformer) components attached may fail.

You may want to investigate using an rx-only antenna port, (changing a menu option possibly) and putting screw-on dummy loads on the main transmit ports. That way you won't damage the rig transmitting into the wrong antenna port, or damaging rx antenna components - accidentally pumping 100 watts into your MFJ receive only loop antenna would be a sad day indeed.

Another trick would be replacing the typical 20 amp fuse in the dc power line, with one that is slightly over your receive-current rating. Perhaps something like a 5 amp fast blow fuse in your dc power lead would provide additional protection from extended transmit.
 
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#5
It could. Then move to the next value up. Sometimes the fuse is faster than the supply.

Sometimes it's human nature after spending big $ on a receiver, and then cheap out on the supply, only to have it crowbar or fail badly damaging the receiver / rig when it is underpowered on purpose. :)

Also note that some OEM supplied matching power supplies weren't of the best quality and got quickly removed from market. Some made obnoxious audible squeals while it switches, or was a total noise source in itself - which was especially troublesome for those using indoor antennas! I don't know what the Icom PS-126 is doing, but I notice it has been discontinued.

I think a 7610 would look good on your desk Ubbe!
 

iMONITOR

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#6
iMonitor - just a general rule of thumb being that for an external power supply you typically want to double the current draw, ie for your 7600 drawing 3.5A max, then a minimum of a 7A power supply is called for. Many will specify an intermittent and continuous draw specification, so be careful not to choose one too small.

A good choice for the older linear type of supply for just that radio would be an Astron 7A, or even better the 12A to handle any other preamps, filters etc that you may add on. Both may also accept any temporary power-on surge by doubling the rating of your receiver current draw.

Not connecting a mic or key to prevent transmitting is also a good idea of course - but fat-fingering a transmit function button to an open antenna port, or one that has rx-only components (like a Par EF-SW rx-only transformer) components attached may fail.

You may want to investigate using an rx-only antenna port, (changing a menu option possibly) and putting screw-on dummy loads on the main transmit ports. That way you won't damage the rig transmitting into the wrong antenna port, or damaging rx antenna components - accidentally pumping 100 watts into your MFJ receive only loop antenna would be a sad day indeed.

Another trick would be replacing the typical 20 amp fuse in the dc power line, with one that is slightly over your receive-current rating. Perhaps something like a 5 amp fast blow fuse in your dc power lead would provide additional protection from extended transmit.
Older transceivers, for example the Yaesu FT101 series and the Kenwood TS520 had built-in power supplies while others required separate outboard supplies. However, older transceivers like those above only received the ham bands. Over the years transceivers, in some cases had extended receive and would cover frequencies of interest to shortwave enthusiasts. You are correct that current draw on receive is much lower than when in transmit mode. I personally prefer having both a ham transceiver (since I'm a ham) and a separate shortwave receiver.
Actually I chose the Astron RS-12M (9A continuous, 12A intermittent) regulated/linear. That gives me enough to run a couple accessories with no worries.

Yes I'm very protective of my receive-only MFJ-1886 loop antenna's preamp! hertzian that's a good idea regarding the dummy loads on the 'transmitting' capable antenna connections. I do use the receive only antenna jack with my loop antennna.
 
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