HL2 transmit problem - relay goes on/off rapidly

[Bill - W2WZ]

I'm just getting my new HL2 going.  It works great on receive.   I've tested it with SparkSDR, quisk and sdr-console.

However, I'm unable to transmit on it without a relay inside the HL2 switching on and off several times a second, starting after a transmit time of  ~10 seconds.  I've got the HL2 hooked up to a dummy load through a Diamond SX-200 wattmeter.   I'm running SparkSDR, with the drive set to 148 and hitting 'tune' in FT8 mode.   The meter shows about 0.4 watts out.  SparkSDR shows 0.5 watts out and an SWR of 1.07 or so.

HL2 temperature while this is happening is ~35-38 degrees.  This appears normalish (to me?), except for the relay sputtering away intermittently.

I'm runing gateware 72p8. The bias was adjusted with the hl2setup program.

Has anyone seen this before?  Did I miss some step in the setup?

Thanks,

Bill / W2WZ

[Steve Haynal]

Hi Bill,

A common reason for relay chatter is TX packets arriving at the HL2 with too much jitter, or time between packets. This can cause the HL2 to think it needs to change back to RX and hence the relay change.

What is your network connection from host PC to HL2 like? Is everything running at least at 100Mbs? You can check the connection speed by the LED status:

https://github.com/softerhardware/Hermes-Lite2/wiki/External-Connections#ethernet

Do you have a wireless link in the path between PC and HL2? This was the cause for chatter for another user as a wifi link can add considerable jitter and latency.

What is your TX buffer latency set to? You can configure this in Quisk->Config-> <Radio Name> -> Hardware -> Tx buffer msec. Does increasing this value to 30 or 40 ms help?

To determine if it is a network issue or hardware issue, can you try TX via the CW key jack. If you ground the tip to force CW TX, do you still have the relay chatter after ~10 seconds of TX?

73,

Steve

kf7o

[Joe LB1HI]

Hi All,

My observation:

It may be useful in searching for the cause.

Disturbed TX signal and relay chatter occurred even when LAN quality was excellent. (1 GB network, tested two different good quality LAN adapters, measured throughput and jitters, tested in connection via router and directly)

Increasing the value of TX buffer latency helped with the relay chatter problem but the signal was still disturbed.

I suppose the reason was a disruption of LAN data traffic generated by the PC itself.

Other measurements showed that during high CPU load, the PING value increased significantly for a while.

(Test platform: E5-2667V2 @ 3.6 GHz, 16 GB four-channel RAM. Fairly efficient. Therefore probably the motherhood issue is the cause).

Bill's cause of jitters suggests a similar cause as it occurs after 10 seconds.

By Bill, this occurs in the ten second of the FT transmission. At this point, FT8 decoding is taking place which generates  increased CPU load.

73, Joe
LB1HI

[Bill - W2WZ]

Steve, Joe:

Thanks for the quick reply!  The radio and raspi-4 are both on GigE, through a desktop GigE switch

(yellow light on the HL2 connector).   I went to try out your suggestions this morning, but the 

problem has mysteriously disappared, at least after 3-4 tests.  That is strange, since it's been

very repeatable over the course of a few days.

However, in the quiet of the morning, I did notice that the laptop style power supply (labeled

13.5V, 5A) is putting out an audible whine on xmit.  Maybe I've got power supply issues?

I will craft a cable from the HL2 to my Samlex 1235M and see if that cures it.

I'd try it out on the air now with the laptop supply,  except that an overnight storm has twisted

my parallel dipole and I've got to sort that out.   It's always something!  I'll let you know what happens.

Thanks,

Bill / W2WZ

[Karl Heinz Kremer]

Bill, 

it may have to do with the CPU load on the Raspberry Pi. I am using a Pi 4 as well, and when I start the web browser, the relays on the HL2 start to chatter. That is with Quisk and WSJT-X - I have not seen the problem when using SSB or CW. I have not played around with the buffer latency, I just don't run other applications when I want to use WSJT-X and Quisk at the same time. 

Karl Heinz - K5KHK

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