Recommendations for a 2M SSB LPA circa 200W... ?

[VK5PJ]

Hello Steve,
I was going to suggest you advertise for one of the ex CH5A amplifiers

The NEC V360 will do 250W all day, runs on 28V and need minimal work. I have been using one for over 6 months now and punish it each weekend with a digital mode on 144MHz.

Probably about 2 hours of prep work BUT you do need to find some RF relays for it. Of course no preamp in there but it is a rock solid performer with no fans needed for general use.

http://www.users.on.net/~pedroj/v360/index.html

Hope you find a suitable amp

Regards,
Peter, vk5pj

[VK2XV]

Peter,

Thanks for the link. Very interesting.

I've been tilting at a few windmills lately. I have emailed TE Systems requesting a clear statement that the advertised 350W for their TE-1452G is PEP for SSB, or maximum carrier power for FM/CW. I also emailed a few O/S suppliers alerting them to the Mirage misleading adverts (says 160W all modes, but only is 110W PEP for SSB).

The local supplier I put down $100 for a Mirage B-2518G was surprised about the 160W/110W discrepancy and kindly offered my deposit back. They felt the RM Italy VLA-200V does a real 200W PEP (for roughly the same price as the B-2518G). I suggested that pending confirmation of that (not just manufacturer's specifications, but real world measurement [i.e., two-tone and a CRO]), that they keep the deposit.

The VLA-200 is advertised on the RM Italy website as...

Supply 12-14 Vc
Input energy / power 24 A
Input energy 1 - 50 W FM
Input energy SSB 2 - 100 W
Output power 200 W
Output power SSB 400 W pep

...so it will be interesting how that all plays out with the local supplier.

Cheers

Steve

[VK3QI]

Steve,

I think you are going to be a little disappointed with the RM results.

The RM amplifier uses a pair of SD1477 devices which are specified at 100 watts each output class C. see:http://www.advancedsemiconductor.com/pdf/sd1477.pdf

So applying the rule of thumb, 200 watts by 2/3, you are going to end up with about 130 watts PEP (2 tone) for a respectable -30 dB IMD.

The problem with all the amp manufacturers is that they tend to specify a single tone peak signal, giving quite large figures that bear no resemblance to a properly tested PEP 2 tone signal.

Whilst it is true that the Mirage amplifier advertisements are misleading, AT LEAST they make a substantial effort to explain the ACTUAL PEP output ratings in their manual.
Very few other manufacturers even bother to mention this fact in either their publicity or manuals!

You will notice that the SD1477 is specified at 100 watts output @ 12.5 volts.

What the manufacturers tend to do is crank up the voltage to 13.8 volts and quote the figures at that voltage!

Cheers

Peter VK3QI

[VK2XV]

I think you are going to be a little disappointed with the RM results.

I'm pretty sure you are right...

The RM amplifier uses a pair of SD1477 devices which are specified at 100 watts each output class C. see:http://www.advancedsemiconductor.com/pdf/sd1477.pdf

So applying the rule of thumb, 200 watts by 2/3, you are going to end up with about 130 watts PEP (2 tone) for a respectable -30 dB IMD.

I found this which tests a HLA-150 (quoted by manufacturer as a 300W PEP unit)...

http://www.w8ji.com/rm_hla-150_test.htm

Doing a rough calc for the 70W transistors used in that unit with the 100W devices used in the VLA-200V and using the roughly 95W PEP figure (for acceptable IMD) obtained by W8JI gives...

PEP = (100/70) * 95 = 136W PEP. This agrees with the figure you give.

The problem with all the amp manufacturers is that they tend to specify a single tone peak signal, giving quite large figures that bear no resemblance to a properly tested PEP 2 tone signal.

And I suspect the ops who say their amps (of the types mentioned here) meet the quoted output power specs are doing the whistle test and reading an average power meter. A whistle can be pretty much tone-like (depending on how wet the whistle is...). What puzzles me is if they do the 'aarrgghh' test then you would expect a lower reading as even this constant audio input has about a 4:1 peak to average ratio...

Whilst it is true that the Mirage amplifier advertisements are misleading, AT LEAST they make a substantial effort to explain the ACTUAL PEP output ratings in their manual. Very few other manufacturers even bother to mention this fact in either their publicity or manuals!

True - but unless the buyer downloaded the user manual before purchase they would be in for a rude shock when they open the box and read the manual. Still, at this stage it looks like the RM specs are worse where a VLA-200V is quoted as 400W PEP, when it appears it can only be a 130W PEP amp.

This is all hard to believe ! These are not new units and have been sold for many years - how come ops are happy with these amps ? Do they really believe they are running the 400W PEP VK limit with these units ? Is the analysis here wrong and is W8JI wrong ?

It seems as though to get a real 200W PEP linear amp I would need to buy a '350W' TE-1452G unit.



Cheers

Steve

[VK2XV]

Well - much to my surprise my email to HRO in the US about the Mirage misleading specs has generated an immediate response - they have updated their website and added the true SSB PEP power for the B-2518G and B-5018G models...

http://www.hamradio.com/detail.cfm?pid=H0-005577

http://www.hamradio.com/detail.cfm?pid=H0-005578

I feel I have done my bit for mankind today...

Steve

[VK3QI]

Steve,

There's every chance that the Italians in the Vatican will nominate you for a sainthood!

Interestingly, I purchased the last of the Tokyo High Power amps HL-510V that was manufactured before they went bust, for the very reason that their specs are much more realistic than most.

That amp uses a pair of MRF151G which are rated at 300watts each @ 175 Mhz (50 volts) , (but will actually give 320 watts @ 140 Mhz).

Applying the 2/3 rule gives a clean (>-30dB IMD) at 400 watts PEP.

That's why I initially said you should look at the Larcan amplifier on offer, as they do provide a clean 200 watts PEP ( but using 50 volts of course!)

You have certainly stirred up some discussion!

Cheers

Peter VK3QI

[VK2XV]

There's every chance that the Italians in the Vatican will nominate you for a sainthood!

Hold the sainthood - send a voucher for a real 200W PEP amp ...

I wonder if the 'optimistic' PEP specs come from an error in understanding what PEP is ?

Reading the term 'Peak Envelope Power' off the page they might be using a CRO for the two-tone test (winding up the drive whilst keeping IMD <30dBc) and measuring 'Peak Power' instead. A reading on a CRO of 100V pk would correspond to 200W peak power in 50 ohms, but the correct value of PEP from that measurement is 100W. For the FM/CW rating they might be just reading an average power meter in 'brick-on-key' mode and winding it up until it saturates which might around the 200W mark.

Just a thought.

Cheers

Steve

[VK4TI]

""snipped""

Hold the sainthood - send a voucher for a real 200W PEP amp ...

I wonder if the 'optimistic' PEP specs come from an error in understanding what PEP is ?

Reading the term 'Peak Envelope Power' off the page they might be using a CRO for the two-tone test (winding up the drive whilst keeping IMD <30dBc) and measuring 'Peak Power' instead. A reading on a CRO of 100V pk would correspond to 200W peak power in 50 ohms, but the correct value of PEP from that measurement is 100W. For the FM/CW rating they might be just reading an average power meter in 'brick-on-key' mode and winding it up until it saturates which might around the 200W mark.

Just a thought.

Cheers

Steve

A lot of marketing happening these days , a gig in marketing is 1000 , not the 1048 we once know , 200 rms in audion might be 800 music power and the same when trying to flog a cheap amp , buyer beware I guess .

[VK2XV]

At least the FT-847 specs on 144MHz make sense. Uses a single 2SC5125 on 144MHz. This is rated as 80W @ 12.5V @ 175MHz. Looking at its Pin/Pout curve reveals it is linear up to about 60W, so the 50W PEP SSB spec @ 13.8V @ 144MHz (Class AB) seems reasonable. Interestingly it looks like it could do >80W on FM (Class C), but may be wound back to the 50W level due to dissipation issues in the confined space - although it does do 100W on lower bands...

Anyway - all will be revealed if the local supplier does a two-tone test on the VLA-200V with a CRO like in the good old days...

[VK3QI]

Steve,

Any reply from the Italians at RM (or from the Pope for that matter!) ?

Any action on the two-tone testing by the local supplier?

Cheers

Peter VK3QI

[VK2XV]

Any reply from the Italians at RM

I didn't ask RMI for any comment - but I did alert HRO (and they changed their website text about Mirage amps from a blanket "160W" to "160W FM/CW & 110W pep SSB/AM"). Further to Mirage I raised a ticket entitled " Misleading advertising" with them. I have had a response which says " we have passed your comments on to the boss.." - but no response yet.

Also no response from the local suppliers re testing RMI amps. I might ring today if I am not grumpy...

The challenges to Mirage and HRO are just windmill-tilting-at. The useful practical exercise is the local testing of the VLA-200Vs.

Cheers

Steve