View Full Version : RM Italy Amplifiers
10-17-2006, 09:24 PM
For the record, I have no intention to purchase or use one, I'm just curious.
Anytime anyone posts a question around this site mentioning one of these things, the near immediate reply is 'they're dirty junk and you shouldn't use them.'
Here's my question:
How do you know that?
Has QST done a review on any of these? Is there a place on the inkernet where I can see test results?
I'm just having a Missouri moment, so show me.
10-17-2006, 10:52 PM
The ARRL Lab wouldn't test an item that's not lawfully available for sale in the United States. RM Italia amplifiers are not certificated for sale here, and cannot be lawfully purchased here, so that negates the need for any product review.
The recent FCC Report & Order that will allow for amateur HF amplifiers that cover the 10m and 12m bands as long as they are not capable of amplifying signals in the 11m band still requires that amplifiers be certificated for sale in the U.S.
The only one I've ever seen up close was a little 250W amplifier advertised as an amateur HF band amplifier, model RM-250 or something similar to that. A neighbor ham picked one up at the TRW Swap Meet for only $50 and thought he had a good deal.
We tried it out using an FT-817 as the exciter, because it only required about 4W drive to make full output. Into my dummy load through a 20 dB directional coupler, further isolated by another 20 dB resistive attenuator, into my HP 141T spectrum analyzer with the 1.2 GHz RF module and standard IF module with selectable filters and video smoothing. It was awful.
At 4W drive power on 40 meters, it made about 200W output power and the output spectrum looked like a comb generator. I think the harmonics up to about 5x were all -20 dBc or stronger. I had no convenient way to measure 3rd-5th-7th-9th order IMD, which would have been a really good test, because that requires multiple low distortion sources I didn't have. But I suspect it would be terrible.
We did measure output power vs. drive power to check for linearity, and it wasn't "linear" above about 100W output, which only required about 1W drive. 20dB gain is interesting to have, but it's only 20dB at very low input levels. Above that, it compresses a great deal, and required ~4W for 200W out. That's 3 dB of compression, which helps explain the harmonic content.
It doesn't have bandswitched low pass filters, which explains why so many harmonics of 7 MHz blow right through it, into the load. Harmonic suppression when driven at 28 MHz was better, and I think the x2 and x3 were around -30 dBc when operated in the linear region, but when driven with a full 4W, that all fell apart and got worse.
Again, only one bench test with only one sample of only one model; but if that's representative of the product family, I wouldn't spend a dime on any of it.
I suspect others have performed similar tests to yield the "don't buy it!" reputation the gear has.
But I doubt the League would bother testing something that technically isn't available for sale here.
They do have some amps for use above 50 mhz and some below,
Ebay is full of these amplifiers everyday. I wonder who is buying all of them? Ebay could care the least what radio item is put up for sale, it is legal in their eyes, as long as it it posted under the ham radio section.
I bet 75% of the amplifiers posted under Ham Radio on Ebay are not FCC certified and legal amplifiers.
What ham in his right mind would buy an amplifier for only 10 meters? That is something I have never figured out.
Quote[/b] ]Ebay is full of these amplifiers everyday. I wonder who is buying all of them?
Easy answer: CBers.
Quote[/b] ]Ebay could care the least what radio item is put up for sale, it is legal in their eyes, as long as it it posted under the ham radio section.
Not true. They WILL pull auctions of such and have done so even in cases where legitimate equipment is up on the block.
Quote[/b] ]I bet 75% of the amplifiers posted under Ham Radio on Ebay are not FCC certified and legal amplifiers.
If they're made by Palomar...Texas Star...Davemade...Skullcracka...and so forth, you're correct. NONE of those amps carry FCC certification that allows them to be legally sold in the U.S.
Quote[/b] ]What ham in his right mind would buy an amplifier for only 10 meters? That is something I have never figured out.
If a person were to convert a CB for use on 10, or had a single-band 10M rig of less than 25w then a set of 'boots' would be helpful in times of bad band conditions - especially when running mobile. One would want the amplifier to be clean - and not a harmonic generator as 'WIK illustrated.
RM Italia - the official amplifier of ALFA TANGO!! http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif