[NLRS] IF radio power consumption

[tom ring]

The 857 can be switched to low power transmit mode by grounding pin 6 (I think) 
of the power connector.  I am not sure exactly what this does to the radio.  It 
may bypass the finals, it may just change the bias and drive.  It puts the 
radio in the same mode as the 897 is when on internal battery power.  My 897 
manual does not mention the transmit current draw in this mode, nor does the 
857 manual.  The receive is .55 squalched, and 1A unsquelched.

After a bit of googling I have found nothing that states what the current draw 
is when in reduced power mode.  I'll check by measuring one or the other, but 
not tonight.

tom
K0TAR


On 20 Sep 2007 at 7:09, John P. Toscano wrote:

> 
> 
> Hello, all.
> 
> My 10 GHz setup is currently powered by a pair of 31 amp-hour gel cell 
> batteries in parallel, which can be charged either by plugging into a 
> home power supply or by using the cigarette lighter socket in the back 
> of my SUV though a "PowerGate" device which isolates the batteries from 
> the vehicle electrical system and limits the charging current to prevent 
> damage to the batteries or the car's electrical system.
> 
> This weekend, unfortunately, I had to run the engine of my car much more 
> than I'd have liked in order to keep the battery voltage from sagging 
> too low. In fact, on a couple of occasions, when I was sending CW 
> beaconing or in a CW QSO, my signal was FM'ing because the battery 
> voltage had dropped too low. This is in spite of using a "battery 
> booster" device, which normally boosts my voltage to 14v or so to keep 
> everything happy, but even it can't cope when the battery voltage falls 
> to 9 volts or so. Donn quipped that I probably used more gas as a fixed 
> station than as a rover. Well, it wasn't quite that bad, but it was 
> definitely not optimal.
> 
> I opted for the pair of 31 amp-hour batteries because their weight (one 
> at a time) is manageable for situations where the rig has to be carried 
> to a setup location that is too far from the vehicle to simply run a 
> power cable from the car. (Hey, I'm an old guy with bad knees. With any 
> luck, you'll get there someday too.)  I guess I could go with a bigger 
> battery that would stay more-or-less permanently in the car. But brute 
> force is not necessarily the best answer -- efficiency might be better.
> 
> My setup uses an Icom IC-706 MkIIg as the IF radio. I am very happy with 
> the performance of this radio in this application, with one big 
> exception. My whole station draws a peak of 30 amps during transmit, and 
> most of that is going to the IC-706.  Yikes, 400 watts of DC power drain 
> to generate a 1.5 watt signal on 10368 MHz! There's got to be a better way.
> 
> I thought about the FT-817, which is designed to run in QRP, and I'm 
> sure that my battery problems would go away if I used this for the IF. 
> But several people told me that they liked the FT-857 a lot better than 
> the FT-817 in this application. That sounded good to me, so I went to 
> Yaesu's web site and downloaded the Operator's Manuals for the FT-857 
> and for the FT-857D. Much to my surprise, the tech specs for the radio 
> state that it draws 22 amps on transmit, which is not much lower than my 
> IC-706.
> 
> Of course, as an IF rig, I only need low power at 144 MHz. My 10 GHz 
> transverter is set up for 1 to 10 watts of drive. The IC-706 seems to 
> draw full DC current even though the 2M output is turned down to this 
> level. Does the FT-857 do better in this regard? I'm hoping that the 22 
> amp figure quoted in the specs is really the maximum current draw at 
> maximum output power, but when the output power is reduced, the current 
> draw actually goes down to something reasonable.
> 
> Can anyone tell me?
> 
> Thanks in advance.
> John (WØJT)
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> NLRS at mailman.qth.net
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> 



-----------------------------------------
Tom Ring K0TAR, ex-WA2PHW  EN34hx
85 Westphalia GL Albert
96 Jetta GL The Intimidator
taring at taring.org

What happens if a big asteroid hits the Earth?  Judging from realistic 
simulations 
involving a sledge hammer and a common laboratory frog, we can assume it will 
be pretty bad.
                - Dave Barry
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