LF: Re: Re: 136kHz WSPR experiment

["Michael Sapp" <wa3tts@verizon.net>]



 Roger & All:  I ran my FT-817 on 137 kHz stateside here to see how well it would work with my W1VD version of the e-probe.  Initially it was 10 to 15 dB down versus my high level LF converter that  uses a level 23 double balanced mixer and 2N5109 preamplifier 

 

I found the FT-817 LF/MF performance improves very nicely when using  a low pass filter at LF/MF that has good pass band 50 ohm return loss ---like a Butterworth LPF with a 500 or 300 kHz cutoff.  About half way through the evening running the e-probe to LPF to FT-817 on 2200m wspr2, I decided to build and add a broadband 2N3904 amplifier stage. An extra 10 dB or so of net gain after my LPF for 137 kHz WSPR2 listening made a large improvement.  I had some +3000 km  decodes from WH2XXP overnight in the mid teens for SNR values, whereas I was having only WSPR2 limit range decodes of WH2XXP without the added preamplifier gain.  Initial FT-817 settings were IPO "off", NB "off" AGC "off."   After adding the broadband 2N3904 preamp I had to run the input attenuator in the FT-817 and had AGC set to fast with about a S3-S4 background level.  It seems some gain is needed to get through the RX front end in the FT-817, but using the attenuator in the radio does not seem to hurt RX performance with about 20dB of total preamp gain. Tonight I hope to add a variable bias resistor to fine tune the preamplifier gain for best FT-817 performance.

 

 I did try playing with the alignment menu setting "01" for .5 to 2 MHz IF gain in the FT-817.  Higher or lower  "01" settings did not make any difference in FT-817 receiver sensitivity at LF/MF.   But having a good 50 ohm Z match with an LPF to the FT-817 appears to be essential for good reception at 137 or 475 kHz....then adding the preamplifier after the LPF makes up for the rx front end deficiencies. My high level converter would still be my preference for performance, but the e-probe>LPF>2N3904 preamp>FT-817 and attenuator worked reasonably well here...

 

73 Mike wa3tts

 

  FT-817 reception overnight on 2200m band

 

2018-01-25 07:48	WH2XXP	0.137507	-18	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 07:52	WH2XXP	0.137507	-19	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 07:44	WH2XXP	0.137507	-20	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 07:56	WH2XXP	0.137507	-20	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 09:00	WH2XXP	0.137507	-21	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 08:56	WH2XXP	0.137507	-22	0	DM33	1	WA3TTS/2	EN90xn	3014	65

 

 

2018-01-25 06:36	WH2XXP	0.137507	-30	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 11:04	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 10:08	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 11:56	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 06:24	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 12:20	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 05:52	WH2XXP	0.137507	-31	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 10:28	WH2XXP	0.137507	-32	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 05:56	WH2XXP	0.137507	-32	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 12:36	WH2XXP	0.137507	-33	0	DM33	1	WA3TTS/2	EN90xn	3014	65
2018-01-25 04:44	WH2XXP	0.137507	-33	0	DM33	1	WA3TTS/2	EN90xn	3014	65

 

 

 

 

 

----- Original Message -----

From: Roger Lapthorn

To: rsgb_lf_group@blacksheep.org ; rsgb_lf_group@yahoogroups.co.uk

Sent: Wednesday, January 24, 2018 4:21 AM

Subject: LF: Re: 136kHz WSPR experiment

Sorry about the spurious "," .

On 24 January 2018 at 09:19, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

A couple of Gs came on. G3XIZ (46km) was 2-3dB better S/N on the earth-electrodes than on the compromise vertical. He is end-on to the "loop" in the ground. G6AVK was not copied at all. He is orthogonal to the "loop" in the ground. I was quite surprised not to spot him at all though.

Conclusions? The earth-electrode "antenna" in the ground is quite effective at 136kHz, but more directional.

Next season I will definitely try an , E-field probe on RX!

No great DX, but experimentation!

73s

Roger G3XBM

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