Poor RX performance

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JohnK1JD
 

Posts: 12
Joined: 27 Apr 2022, 12:54

Poor RX performance

Post by JohnK1JD »

My radio arrived a few days ago, and I’m new to this forum. After a few minutes with the radio using a LiPo 3S for power and my station antennas, the receiver on CW is a disappointment because of many spurious signals. The spurs tune in the opposite direction as actual signals on the bands. I heard these spurs initially with no antenna connected and figured that band noise would be greater, but this is not the case. I would like to know if this behavior is normal or if this particular radio isn’t working properly. I can provide an audio recording if that helps.
73,
John K1JD
Santa Fe, NM
AC9YY
 

Posts: 133
Joined: 21 Mar 2022, 00:04
Location: Illinois, USA

Re: Poor RX performance

Post by AC9YY »

John,

I know there were reports of a small number of spurious signals, but not a lot. Generally for me the band noise is higher than the noise floor and most spurious signals. Can you provide more details?

Jim
JohnK1JD
 

Posts: 12
Joined: 27 Apr 2022, 12:54

Re: Poor RX performance

Post by JohnK1JD »

Yes Jim, I’ll take the time to make recordings/videos. To be clear, this radio was not a kit so it doesn’t really belong under “troubleshooting”.
As a SOTA activator with 700 summits, I have a lot of experience with tiny, lightweight QRP radios (KD1JV, QCX, etc) all built by me but decided to purchase this one already assembled.

73,
John K1JD
AC9YY
 

Posts: 133
Joined: 21 Mar 2022, 00:04
Location: Illinois, USA

Re: Poor RX performance

Post by AC9YY »

JohnK1JD wrote: 27 May 2022, 12:10 Yes Jim, I’ll take the time to make recordings/videos. To be clear, this radio was not a kit so it doesn’t really belong under “troubleshooting”.
As a SOTA activator with 700 summits, I have a lot of experience with tiny, lightweight QRP radios (KD1JV, QCX, etc) all built by me but decided to purchase this one already assembled.

73,
John K1JD
John,

If you purchased from the approved vendor they have really good support if you contact them. I just hooked up my built unit to a dummy load and using USB I checked most of the 20 meter band and I generally am seeing -113 to -104 dBm. Are your readings comparable? For comparison the noise floor is 20-25 dB higher than my Xiegu G90 assuming both meters are accurate.
73,
Jim AC9YY
JohnK1JD
 

Posts: 12
Joined: 27 Apr 2022, 12:54

Re: Poor RX performance

Post by JohnK1JD »

Spent some time yesterday looking closely at spurious signals and RX performance in general. Overall, there isn’t really anything too severe at work here. For the price of the radio it’s pretty good!
To start I compared the 20m uSDX and Elecraft K4D noise levels according to the built in measurements in each radio. Not that anyone would expect it to be a fair comparison, just wanted a few data points. The radios with antenna connected (quiet QRG) were 104dBm uSDX and -123 K4D. With a dummy load, -107 uSDX and -128 K4D.
Looking at spurs on 20m, there are 4 of them in the SOTA QRP window from 14.060 to 14.066, the strongest is on 14.063 at -102 dBm. The others are -104 or less. All can be heard while copying stations but only 14.063 might compromise the ability to copy a very weak station.
Spurs on 40m and 30m are far less of an issue. On 30m, there’s a -102 spur on 10104.2, several others are -104 and less noticeable. The BIG spur is -95 dBm at 10125.8, very strong but it’s out of way for most CW SOTA ops. On 40m, there are 7 spurs between 7.027 and 7.059. Two are very strong, one at 7.027 is -90 and the other at 7.059 is -85. The next strongest is st 7.032, -104 which was at the time of measurement 3dB above the noise floor.
The major drawback for SOTA use is insufficient display brightness. Since most everything is menu driven, one must be able to read it in full sun. I’ll be reading up on mods to make it brighter.
73,
John K1JD
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