Microset 27-200T H.F P.A

[VK2AOH]

These are a H.F solid state amp which in their specifications indicate they cover bands 80/40/20/15 and 10 metres. However there is nothing in the specs about the WARC bands 30/17 and 12 metres.

I would presume the amp should cover the WARC bands however before going ahead with purchasing one hoping someone has one of these whom has actually used these amps.

The only op I know whom has one can only use it on the standard bands.

Being a 12v powered device it would be handy for camping trips where a bit more punch would be possible given the poor state of the bands as of late.

There are a number of times my KX3 just does not have enough grunt.

http://www.microset.net/componenti.php? ... 86&lang=en

Thanks for any information.

[VK6ZFG]

Must be using breakthrough technology to achieve the incredibly high efficiency based on the published output power vs the input power figures.

From what I can see it does not appear to incorporate filters. If this is so and used like this it would would contradict the amateur operating LCDs. Worth some further investigation.

[VK4ADC]

From what I can see it does not appear to incorporate filters. If this is so and used like this it would would contradict the amateur operating LCDs. Worth some further investigation.

That statement could do with a bit of refinement. The LCD states that any spurious or harmonic content must be below -43dBc for transmitters below 30 MHz and if the amplifier is truly linear, however unlikely, then the signals at additional frequencies are determined by the output spectrum of the K3 transmitter itself.

If the amp is somewhat or significantly non-linear, the possible lack of output LPFs would then be significant.

As Roger 2ZRH would add :
Posted in the interests of stirring the pot.

Doug

[VK2AOH]

Thanks for the comments so far, all noted and had some concerns myself on the lack of filters. Should have mentioned I always have a autotuner between the KX3 my current 50W el cheapo chinese PA and the aerial.

(the chinese P.A does have switch selectable output filters).

Being in a suburban area don't want to take any chances.

From what I can make out these Italian amps are sold in UK and Europe and the lack of information on WARC bands makes me wonder a bit.

With the popularity at least of 30M in Europe one would imagine that things like this would be used by the more portable type of operator on field excursions.

Anyhow will wait and see if someone pops up whom actually uses one.

[VK6ZFG]

I have a chinese MX-50P and and so far has perfomed OK. It does include filtering but requires manual switching. Heat sinking is a bit light on for any serious operating but then it is quite compact so you can't have everything. Power output approaches what is claimed.

I have been unable to find any real technical details on the 27-200T. One reference had them using MRF451 transistors but these are only rated at 80W max so it is doubtful this is correct.

The lack of band selection switch on the 27-200T amplifier or mention of automatic filter selection to me implies that no filtering is present. This would of course mean that it would work on any HF frequency between 3-30MHz.
The amplifier will however introduce increased the harmonic content from that of the input signal. This will depend on the devices used in the amplifier, how hard they are driven etc etc.

As a quick reference I looked up a Motorola Application Note for a 160W 3-30 MHz RF power amplifier. This had the 2nd harmonic as low as -15dB, 3rd _20dB, 4th -21dB so filtering would clearly be inorder.

By the way the Amateur LCD requirements on spurious output is:

"
7A Spurious emission limits for an amateur station

(1) The licensee must not operate an amateur station if the emissions of the station include spurious emissions that are not attenuated below the power of the wanted emission supplied to the antenna transmission line by:
(a) for frequencies less than 30 MHz — the lesser of:

(i) 43 + 10 log (PEP) dB; and
(ii) 50 dB; or

(b) for frequencies equal to or greater than 30 MHz — the lesser of:
(i) 43 + 10 log (P) dB; and
(ii) 70 dB.

(2) In subsection (1):
P means mean power in watts supplied to the antenna transmission line.
PEP means peak envelope power in watts supplied to the antenna transmission line.
"

This means that the 50dB requirement applies above the 5W level below 30MHz.

[VK6ZFG]

From from additional reports on the internet I have managed to find it would appear that the amplifier may be using RF power transistor series covered in Motorola Application Note an762 with a pair of MRF454 most likely type.

A pair of MRF454 is rated at the best at 140W. A pair of the highest rated MRF421 ups this to 180W. The Application Note gives the 3nd harmonic level varying with frequency but could be as high as -15dB. 2nd harmonic not being a problem as a push-pull configuration is used. Efficiency is stated as between 40 and 65%.

If the above is correct I find it hard to relate it to the amplifier manufacturer released data.

I suspect may be a CB type amplifier.

[VK2AOH]

The 50W P.A I have is one of those chinese MX-P50M's with switchable filters. Not a bad little amp although as has been remarked can get mighty hot if run for prolonged calling.

Put a fan on mine which helped a lot.

As for the Microset amp am pretty sure it uses MRF 454's. The amps are sold in UK and EU as I have mentioned but any actual users comments are scant or non existant. Despite much searching.

Sets of harmonic filters would be a good thing.