Severe RX attenuation and high SWR issues on 20m band (ONLY) with HL2 + N2ADR / PA100

[Paul Cristea]

Hi everyone,

I'm facing a frustrating issue with my Hermes-Lite 2 setup combined with an N2ADR filter board and a PA100 amplifier, specifically affecting the 20m band. I would appreciate some guidance or advice from anyone who might have encountered something similar.

The Problem:

• I am experiencing very heavy RX signal attenuation exclusively on the 20m band.

• When attempting to transmit on 20m, I am getting abnormally high SWR >3.3 readings.

• Other bands seem to be operating normally, leading me to suspect an issue within the specific filtering or switching circuitry for the 20m band.

Troubleshooting Done So Far:

1. Antenna & Load Tests: I initially suspected my JPC-12 vertical antenna or its contacts, but testing the setup into a known good dummy load yields the same problematic behavior on 20m. Testing RX with a simple random wire also shows the same heavy attenuation.

2. Visual and Relay Inspection: I've looked closely at the N2ADR board and PA100 integration. I suspect a potential relay switching fault or a component failure in the 20m low-pass/band-pass filter section. But in 30m (same path filter everything working ok)

3. Component Check: Looking at the N2ADR schematics, I have been eyeing the capacitors in the 20m filter path (specifically checking around C17, C19, and C22) for any signs of physical damage or SMD failure, but haven't definitively found the culprit yet.

Before I start desoldering components or replacing relays blindly, has anyone seen this specific failure mode on 20m? Are there specific voltage test points or control signals I should verify on the N2ADR board to confirm if the correct relays are engaging for 20m?

Any schematics tips or debugging steps would be highly appreciated.

73,

[John Williams]

Are your band selection checkboxes set properly for the n2adr board. As a test into a dummy load, set the filter for the 20m band the same as the 17/15 setup to see if you get relief. My bet is a stuck 20m relay. That doesn't explain the 30m result. 

Sent from my iPhone

On Jun 29, 2026, at 9:33 AM, Paul Cristea <yo2...@gmail.com> wrote:



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[John Williams]

Remove the amp and test barefoot.

Sent from my iPhone

On Jun 29, 2026, at 9:48 AM, John Williams <JSWI...@gmail.com> wrote:

Are your band selection checkboxes set properly for the n2adr board. As a test into a dummy load, set the filter for the 20m band the same as the 17/15 setup to see if you get relief. My bet is a stuck 20m relay. That doesn't explain the 30m result. 

[Steve Haynal]

Hi YO2CPS,

Yes, please check your software settings and try different software first. Then, isolate the problem by removing the amp, and then removing the N2ADR board, etc. Search this group for RX problems. There is a recent thread going through all the steps.

73,

Steve

kf7o