Problem with PA HLA 300V Black

[DJ9FBA Franz]

Hello Steve, I have a problem with a power amplifier called hla300v black from rm italy. When I send in SSB, a distorted echo can be heard in the signal and the original audio is totally distorted. The drive power of the Hermes Lite 2 is two watts, the output of the PA is around 120 watts. Is this perhaps a direct radiation into the Hermes Lite 2. 73 de dj9fba

[Dan Cusick]

I have an RM Italy 305

It has 4x MRF455 m/com npn rf power transistors.  When working it produces 240w.  The circuits in these are super sensitive to swr and not well protected.  Its likely your amp is 1/2 blown.

73,

Dan

W9IRL

On Fri, Mar 15, 2024 at 3:00 PM DJ9FBA Franz <dj9...@gmail.com> wrote:

Hello Steve, I have a problem with a power amplifier called hla300v black from rm italy. When I send in SSB, a distorted echo can be heard in the signal and the original audio is totally distorted. The drive power of the Hermes Lite 2 is two watts, the output of the PA is around 120 watts. Is this perhaps a direct radiation into the Hermes Lite 2. 73 de dj9fba

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[DJ9FBA Franz]

The Amplifier work very fine with another Trx  as Icom Ic 7610 or with Yaesu Ft-101D. With these transceiver i have not this Audio Echo problem
 73 Franz dj9fba

[Ezio Insinna]

Hello Franz,

Have you measured the SWR between the HL2 output and the HLA300 ? 

I had a similar problem. I guess there is a mismatch between the HL2 and the PA and this causes oscillations in the HLA. The input stages are not very well

tuned and these amps are prone to oscillations with some rigs.

Try to put a 3dB (50 Ohm) attenuator in line between the two and raise the drive power to 4W on the HL2 and see what happens.

The attenuator divides it by factor 2, but it allows you to reduce the mismatch.

73

Ezio - K3EK / F5MWA

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[Ron Lewkowicz]

I would imagine distorted audio would be a result of over driven audio settings in your software. The echo is also likely due to software with some monitor setting or duplex setting.  There is buffering in the software that will cause a delay so you don't want to monitor your TX audio there.  2W in 120W out sounds about right for that amp.  A 5W tune signal into HLA-305V gives me well over 200W out.