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Ft817 or ft818


Sorry. I should have checked my log! Glad everyone is paying attention!


You need to be a bit more specific.

There are plenty of MM (Microwave Modules) amps about secondhand. They normally need 1 or 3W dirve and produce 25/30W. Most were designed when the FT290/FT790 was the rig to own. Some designs are dated but still very effective. Some were updated in the 90s when MM was restarted.

MM 144/25 is 2m, 25W out for 2.5W drive with preamp. The preamp cannot be switched out.
MM 144/30-LS is 2m 30W out for 1or3W drive with switchable preamp.
MM 432/30-LS is 70cms 30W out for 1or3W drive with switchable preamp.

Ebay prices are stupid but there are nearly always plenty waiting to be sold or at rallies. Placing wanted ads on some of the equipment sale websites (not ebay) would bring results.

My 432/30-LS was bought at Blackpool in 2013 for the massive sum of £30 and it had been looked after, not a mark on it despite being 20yrs old.

The real world prices are about £0.75/W for MM 144 amps and £1.15/W for MM 432 amps. Of course now ebay recommends prices, clean FT290s are being listed at £150+ which is crazy money.

There are new amps still. And there are tatty Chinese amps. Some DIY amp kits on ebay are good value but you need a small amount of clue to build and box them and YOU NEED SOME KIND OF LOW PASS OUTPUT FILTER which is normally not in the kit.

This 144/30-LS is on ebay, 173891804725, but at 3x what it’s worth. The power supply being offered is worth £5 secondhand.


Often feel at RX KX3 needs 220 mA but my FT817 350 mA.
This means that after 3 hours of RX my FT817 consumes more 0.39 AH.
Miracle on SOTA ?

73 Miro OM7SM


Yes sorry more specific , a 2m linear ideally and any power output as long over 20w and below 50w with being kind to a battery also .

Matt 2E0FGX


It depends on how you run your 857. The handbook gives a squelched consumption of 550 mA and 1 amp on receive, I find mine takes about 600 mA on receive into headphones. Similarly, the 817 handbook gives 250 mA squelched and 450 mA on receive but into headphones mine takes about 300 mA. The KX3 is a fine little rig but the 817 seems more sturdy and in some ways is more flexible, but in the end of the day it comes down to personal choice.


That’s a good point well made! It is easy to overlook the power used (wasted) in driving a loudspeaker, especially if you have the volume up full to overcome wind noise.
Measuring the current drawn as you adjust the volume is an easy bench experiment to carry out, if you have any doubts :smile:


At best a 25W amp will be about 40% efficient, probably less. @13.5V it will need about means about 4.6A of current. Peak for SSB and continuous for FM. As your voltage drops as the battery discharges then the linearity will get worse as will the gain. i.e. you’ll be a more splattery signal at a lower output.

Also some amps will have a higher standing bias current, so when the amp is on standby, it will be pulling maybe 500mA+ before you need 4A+ of current to amplify the signal.

“You canny break the laws of physics”.


During the recent VK/ZL/JA//EU day, even using the CW and FT8 modes, an FT-817 was no match for an FT-857 working ssb. Remember, your rig is only part of the radio conundrum, your antenna choice is far more important.

Have fun…


Yes thats so true , this is why i always seem to plsy around with antennas more

I would be using a external battery so can talor ah to the linear used

Matt 2E0FGX


But an FT-857 using CW or FT8 would be even better!

Walt (G3NYY)


They are very much the mutz for FT8 when run up to near 75-80W.


The implied punchline to that was “even when the the competition is better and cheaper.”



Only if they’re using the right antenna, Walt :wink:

73 Mickey


There are so many right answers, and if the ionosphere isn’t playing ball, they all become wrong answers!


Hi Brian,
By squelched, does it mean fully cut off, as in an FM rx squelch function? Is that relevant to HF SSB operation, I somehow doubt it, squelch ruins any attempt at weak signal reception. So is the ssb rx current = 1amp?

When you plug in headphones, does that turn off the DC to the audio chip? I haven’t seen that in any rig. If not, it is drawing its bias current plus any current due to signal levels, assuming AB1 or class B. Try plugging in the headphones while a tone is being received, monitor DC consumption. I can do that with my rigs, if wx ok I will do it with the kx3 today. I have a watts-up monitor.

Andrew VK1DA/VK2UH


Hi, Andrew. I just quoted the handbook FWIW! As I said, mine takes about a measured 600 mA when I’m using headphones and listening to a station at a comfortable level. I don’t know if the AF chip is disabled - I don’t know if you have seen the circuit diagram, it is so crammed and even disorderly that it tends to defeat my eyes, and as it is after local midnight here I will defer having a good look at it, I hear the siren tones of my bed summoning me!


"Used FT817
“You may need to spend time finding a good one.
There may not be a warranty.”

Adrian, based on the few Yaesu warranties I have read, they are void for anyone but the original purchaser… and my occupation is fine print.

Elliott, K6EL


Yaesu UK (and possibly other European offices) tend to honour warranty periods even if you’re not the original purchaser. It’s one of the reasons equipment often costs more than in the USA.


Elliott, Andy, thanks for the comments, interesting!
I was thinking rather less specifically that if you buy used equipment from a reputable dealer, there is likely to be some level of after sales support albeit with fine print to check.
But if you buy from a private seller you are probably buying “as seen” with no comeback. Of course, there will (should) be a price difference to reflect this…


Often very large.