Replacement of T2 for LF and MF sensitivity.

[K H]

Hello,

I'm testing HL2 on 2200m and 630m band. It seems OK but the SNR of WSPR is a few dB less than the other SDR "Airspy HF+Discovery". Both are connected to the PA0RDT type miniwhip antenna through the 2 port divider.

I found the modification of "T2" (the frontend transformer) for better sensitivity issued by IN3OTD. I have a BN73-202 instead of BN73-2402 so I try to replace "T2". The BN73-202 is bigger version of BN73-2402 and the specification is the same I think.

But it seems difficut to desolder from the PCB. So I must be careful.

My HL2 is build-9 and is this effective for LF and MF receiving?

Any suggestions are welcome.

73, JA9MAT Hidehiko.

PS: I wonder why HL2 uses MABA-010143-FLUX18 despite the coverage from 2MHz to 500MHz? HL2 needs to modify to cover low band.

[Steve Haynal]

Hi Hidehiko,

The HL2 is only stated to cover down to 160M. The smaller MABA-010143-FLUX18 device is less expensive for automatic assembly. There can be a lot of noise and QRM in the AM band and lower which can overload the ADC. For these reasons the standard HL2 is not designed for lower than 1.8MHz. The HL2 can be modified for use at 1.8MHz and below. You found the recommended modification for T2. Hot air is the best to remove the existing T2. You may also have to reduce QRM at your QTH for best results.

73,

Steve

kf7o

[K H]

Hello Steve,

Thanks for nice project.

I've just replaced T2 to BN73-202. It's really bigger than the original T2. hi...

It seems that the reception is better at 40kHz and 60kHz time standard signal (JJY) but the less at over 18MHz. It is the specific of this core. BN73-202 is good at low frequency.

Yes, I understand the concept of HL2. The original T2 is good for HAM transceiver. But I mostly use the HL2 for receiving 2200m  and 630m band WSPR and FST/4W digital mode. The SparkSDR is very good for receiving standalone.

Anyway I will test tonight at 2200m and 630m band and report the result. 

Thanks again,73.

JA9MAT Hidehiko.

[K H]

The result of comparison is as follows;

1) SNR: 1 or 2 dB up at 2200m and 630m band - better than the original

2) But I feel the less sensitivity over 17m band - 2 or 3dB less than the origial

3) Around -120dBm from my hp SG can be heard on all band - the same with the original

This is trade off.

I will keep listening for a week and consider whether back the original T2 in place or not.

Hidehiko JA9MAT.

On Tuesday, September 14, 2021 at 1:22:02 PM UTC+9 softerh...@gmail.com wrote:

[Steve Haynal]

Hi Hidehiko,

Thanks for the report. It is interesting to hear how well or poorly the HL2 does on 2200M and 630M with the replaced T2.

73,

Steve

kf7o