Those 10 Meter - Ahem! - mobile Amps

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=290164311747&ssPageName=STRK:MEWA:IT&ih=019

These 11M amps are advertised as pretty hefty power output amps. Price is fairly small. Has anyone tried to modify these to 40M or 80M where a ham could really use the added power? Seems like a bias change here and a tuned circuit change there and it should be in business on a better place.

[kc2orw]

I would worry that they are all cheap junk and it might be better to pick a kit or a known homebrew circuit. Sometimes it is just hard or near impossible to modify junk like this so...

PS: It is possible that such an amp could have some re-usable components but is it cheaper to buy this or just buy the components?

I would worry that they are all cheap junk and it might be better to pick a kit or a known homebrew circuit. Sometimes it is just hard or near impossible to modify junk like this so...

PS: It is possible that such an amp could have some re-usable components but is it cheaper to buy this or just buy the components?

Specifically, I cannot find the price of these transistors. I find some similar to these, and they are around $40 to $50 apiece. So yeah. I am looking for parts, mostly.

Just poking around right now.

[kc2orw]

Specifically, I cannot find the price of these transistors. I find some similar to these, and they are around $40 to $50 apiece. So yeah. I am looking for parts, mostly.

Just poking around right now.
Sure who knows the unit price might work out favorably just for the parts?


http://www.amateurlinearamplifiers.com. ... words=0595 (http://www.amateurlinearamplifiers.com./cgi-bin/cart.cgi?user=070927175855&action=subcatdisplay&words=0595)
http://www.digikey.com/scripts/dksearch ... 97-5458-ND (http://www.digikey.com/scripts/dksearch/dksus.dll?Detail?name=497-5458-ND)

[N3ATS]

SD1446 are cheapo transistors. See if you can find any 2SC2879. Get 32 of 'em and build yerself a maul droppa! :lol:

Thanks for the links ORW. Seems like to me getting the unit ready to go for 10M and converting it to 40M is easier and cheaper than building from scratch.

Where can I find a source for the 2SC2879? The SD1446 seems to add up pretty fast.

[n8ats]

i talk to a guy on 75 that use to drive truck, and he ran one of the skywalker kit amps built for 11m use. to make it work down on 75, he rewound his input and output transistors and talked away with it.

i talk to a guy on 75 that use to drive truck, and he ran one of the skywalker kit amps built for 11m use. to make it work down on 75, he rewound his input and output transistors and talked away with it.
I think you mean transformers? I hope.

Yeah. I did not see the problem with that proposal.

[KA5PIU]

Hello.

I got some Texas Star amps cheap a while back.
The Texas Star amps are normally class C units with no filtering.
I think of them as a gain block.
For FM and CW they are OK, but in AM service they can excel, I add a pi filter network on the output, and modulate the final transistors.
I also have added a selector for internal or external source, thus it can be a complete transmitter as well as the TR switch.
Coupled with a QRP rig, it is not a bad 10 to 12 meter transmitter.
I fabricated a larger cover to contain the added circuits.
For a modulation amp, a cheap car audio unit is used.
The QRP rig is usually a converted CB radio, or something like an "export" radio.
But, except for the mechanical construction, well built, and they have quality glass epoxy boards, excellent switches, and a good heat sink, there is not much to them.

[N9FE]

You can use em, But you better check your "width" on a scope, you come on splattering like hell your going to get a toot from riley, get an ameritron 500m all bands,, Nice and CLEAN,,, No Worry's.. Better off in the long run, There are 500m's out there with years of pounding on them and still going like new....

[KA5PIU]

Hello.

Yes, the amps as supplied are not that bad.
What happens is that the CB shop adds "swing" and cuts the carrier level in the radio.
This adds "talk power" at the expense of range and creates splatter.
The radio will splatter even without an amp.
The fact that I am actually modulating the amp also helps.
So far a spectrum analyzer shows a super clean signal on AM or DSRC/SSRC.
I do not do SSB no carrier with it nor intend to.
I have added the bias board, for class AB, but have found it unneeded as this can run class C just fine.
And, remember, it is just that, a class C amp with no high pass filter.

[N3ATS]

You wanna see a filthy radio on a spec analyzer? Look at a IC706MKIIG. Spurs everywhere.

[KF2M]

You wanna see a filthy radio on a spec analyzer? Look at a IC706MKIIG. Spurs everywhere.

Ouch.. I own one. Can this unit be cleaned up?

Spurs are difficult to fix. The radio needs to be properly designed from the start, but they probably have some stages in there that are inherently overdriven and will require re-evaluating their biasing. Real good luck in doing that and especially if it is embedded in a BGA IC or some such impossible rectification.

When I was looking for a new rig, the IC706MKIIG was near my short list but not quite there. After reading a few reviews, it was not even close. I can live with a lot of things, but poor performance is pretty bad.

[N3ATS]

You wanna see a filthy radio on a spec analyzer? Look at a IC706MKIIG. Spurs everywhere.

Ouch.. I own one. Can this unit be cleaned up?

Not sure. I never bothered with it. I will say it wasn't tweaked or golden screwdrivered. It was like that out of the box.

[HUGH]

If you see a cheap "11m" amp, buy it. At least you'll get a heatsink and rudimentary case which you could use to make anything, even a dummy load at worst.

[wd0ct]

Hello.

I got some Texas Star amps cheap a while back.
The Texas Star amps are normally class C units with no filtering.
I think of them as a gain block.
For FM and CW they are OK, but in AM service they can excel, I add a pi filter network on the output, and modulate the final transistors.
I also have added a selector for internal or external source, thus it can be a complete transmitter as well as the TR switch.
Coupled with a QRP rig, it is not a bad 10 to 12 meter transmitter.
I fabricated a larger cover to contain the added circuits.
For a modulation amp, a cheap car audio unit is used.
The QRP rig is usually a converted CB radio, or something like an "export" radio.
But, except for the mechanical construction, well built, and they have quality glass epoxy boards, excellent switches, and a good heat sink, there is not much to them.

I think I read somewhere long ago that some texas star are AB biased. One of those might be okay on ssb if not over driven...