Question about the PA

[Dani]

In the Hermesliste.pdf schematic there is a build option mentioned for the RD15HVF1.

Is the 200 mA bias max and how high would be the max P-Out with proper cooling?
15W?

If I install the RD15HVF1, then what about the bias calibrating? With quisk or the hl2setup but with bias 200 instead of 100?

Thanks.

[James Ahlstrom]

Hello Dani,

I don't think the RD15HVF1 is an option because I don't think the bias circuit can provide enough voltage. The power output is determined by the supply voltage, so you would have the same 5 Watt output. And the bias calibration would not change.

Jim

N2ADR

[Dani]

Hello James,

thanks for your answers!

In the schematic it the following noted:
Set R127,R70 to 7.5K, R47,R66 to 3.3K for bias voltage range from 3.1 to 5.3V

I could adjust the resistors for a bias voltage of 12v?

[in3otd]

Hello Dani,
the RD15HVF1 was tried in an early prototype of the H-L PA; if I recall correctly it did not bring any big advantage w.r.t the current PA with the AFT05MS003N and could actually be not as stable and could oscillate in some conditions.
As you saw the bias circuit can be modified to provide a bias voltage in the range needed by the RD15HVF1 gates; while this bias circuit configuration has been simulated I don't think it has actually been verified in practice.
You can, and actually should, use a 12 V (or up to 13.6 V) drain supply for the RD15HVF1 to get more output power in the lower HF; if you increase the PA driver gain, at 1.8 MHz with 13.6 V of drain supply you can get more than 20 W at 1 dB compression but at 30 MHz you'll get only about 10 W at 1 dB compression.

For reference here below is a graph of the output power measured for an H-Lv2b2 a RD15HVF1 PA (I think this was at 12 V drain supply)

and for comparison what was obtained with the current PA configuration at 7.5 V drain supply. Note that this is not exactly the current PA on the H-Lv2, as its drain supply there is 8 V and the driver gain was lowered a bit but should not bee too different.

In case you want to do some experiments with a RD15HVF1 PA I can try to dig out more measured data and build info.

73 de Claudio, IN3OTD / DK1CG

[Steve Haynal]

Hi Dani,

Yes, you can adjust the bias range per the instructions on the schematic. Also, for RD15HVF1 you leave off all the circuitry for the VPA 8.0V supply and jumper J6 so that VPA is the same as the external power supply voltage, 12V to 13.6V per Claudio's recommendations. Also, you increase the PA driver by adjusting the value of R55. Search this list for R55 or see the OPA2677 datasheet for more details. 

I think Claudio is the only one to test the RD15HVF1 option. Are you after more power? The current LDMOS devices work well, generate less heat, and cost less.

73,

Steve

kf7o

[Dani]

Hi Claudio and Steve,

Claudio thanks for the shared informations, I may be interested in the future.

Steve yes I'm after more power.

Anyone has experience with the Munin 3 PA?

Maybe that PA would work good with the HL2.

Or any other suggestion for a 100w PA?

Actually a 30w PA would be enough....

Munin 3:

http://www.k9ivb.net/Munin3/index.htm

Possible LPF match:

https://www.ebay.de/itm/LPF-HF-50MHz-for-100W-SSPA-RD70HHF1-RD100HHF1-Low-Pass-Filter/332597645483?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

[Jack Generaux]

A friend and I built the previous incarnation of the Munin.  Works quite well on the bench, but I haven't finished the LPF switching (using a HFProjects lp100.)  Other projects got in the way of finalizing -- maybe this winter.

73

Jack (W0FNQ)

[Steve Haynal]

Hi Dani,

The Hardrock-50 has been used with the Hermes-Lite: https://www.hobbypcb.com/products/hf-radio/hardrock-50-hf-power-amp

There is also this interesting amp, which as far as I can tell is a copy of a Yaseu PA: http://ody-sdr.com/2018/09/03/hfpu-100-the-amplifier-for-odyssey-2/

73,

Steve

kf7o

[Dani]

Hi Steve,

the HFPU looks very interesting, thanks!

73 de Daniel DJ6DB

[Steve Haynal]

Hi Dani,

I've also always wondered how the HF amps advertised on e-bay and aliexpress would work in practice:

https://www.aliexpress.com/item/Free-Shipping-3-30Mhz-HF-Amplifier-300-Watt-SSB-Output-power/748704056.html

You'd have to add your own filters.

73,

Steve

kf7o