SW2 manual notch filters and UK VDSL tones

Thanks heavens for the notch filters in SW2! I’ve been trying to work V79XF on 10124.000 with a -90dBm VDSL noise floor which he is just about level with, but with a -74dBm VDSL training tone on 10123.991, that is NINE HERTZ LF of him, and another 4Hz LF of that which is -71dBm.

Without the filters, there is nothing apart from the tones, but a 10Hz wide manual notch set on 10123.987 kills the tones completely and lets me pull him out when the noise floor drops a little.

OK, I feel silly giving a 279 or 389 report, but my neighbours’ VDSL mush makes 30m a solid wall of noise with training tones every 4kHz.

Prologix GPIB-USB interface

I ordered the Prologix GPIB-USB Controller from SGLabs in Italy on Friday 11th March via ebay and it arrived today (Monday 14th March).  Impressively fast.

Bought it mostly because it was yellow.

Works really well with my 8562A spectrum analyser, but I haven’t received the GPIB cables I ordered from a UK supplier before placing the order with SGLabs, so only one device at a time for now…

Here’s a quick test of an FSK441 signal on 1296.200 MHz as received off-air by the 8562A, programmed using the KE5FX utilities:

talk 18 "IP;FA 1296.210 MHz;FB 1296.230 MHZ;LG 10 DB;RL -20 DB;RB 100 HZ;AT 0 DB;KSb;KSS;"
start ssm 18 -M -f -cs -w -t






More detailed testing to follow….

VDSL interference on 10MHz

I’m being plagued by broadband hash right across the 10MHz band apart from one small gap.  (ignore the yellow swooshy thing, that is a real signal).  There are 4kHz wide blocks of the hash, mostly light blue in the waterfalls (which are upwards-moving, with newest at the bottom).

I suspect local copper broadband, we recently got FTTC in the village, however, the noise doesn’t change at all when I disconnect and power off my VDSL modem….


Time for a little experiment.  10s of a 50 watt carrier around 10115kHz.  Interesting, a wide swathe of the noise just disappears for 5-6 seconds, to be replaced with tones at roughly 4kHz intervals.  Then a few segments of hash come back, then more at 12s, and after 20s, some of the pilot tones go away, but not the close-in ones, they stay around for a long time.


It seems to be repeatable, but shorter transmissions don’t get rid of the noises for 12s, just 6s, and under a second of carrier has no visible effect.

So, let’s try calling CQ for a minute or so, with some 5-6 second gaps to listen.  Hmm, looks like I can knock quite a decent hole in the noise.


The hash stops at 12MHz.

ELAD FDM-DUO macros for reference

2m MS;LP1;TI2;AN2;AT0;FA00014370000;MD2;CG000;GC0;GS020;NC000;OV0+00130000000;OS1;RA00;TT1;TB009;VT063;MT10;
No offset;OS0;
CW MSG 1;SW0011;

Testing my unlocked Elad FDM-DUO on 144MHz

Test with unlocked DUO as a standalone 144MHz receiver, 144.002MHz, 100Hz BW, CW, using my DXing ears and Heil Pro7 earphones as a detector, I can hear down to -132dBm using my E4421B with additional 30dB attenuator as a source.

When I compare with my Kuhne TR144H transverter into the DUO, the MDS using the same ears is -156dBm. Perhaps with a good masthead preamp the DUO might be OK for 144. Using WSJT JT4A mode or PI-RX I can hear down to -163dBm with the Kuhne and no LNA.

Works fine in SW2 on WBFM 88-108MHz, but I can’t see any signals in 144MHz, and more worrying, I don’t see any increase in noise when I enable my masthead LNA. I *can* hear meteor pings from GRAVES on 143.050 with the preamp enabled, but the noise floor with or without the antenna plus LNA is unchanged.

On GB3VHF, with the LNA and DUO I get *some* JT65B decodes at 281km, but it is right at the limit of decodability

003400 1 -20 1.1 -5 3 * GB3VHF JO01EH
003800 2 -20 1.1 -5 3 * GB3VHF JO01EH

Certainly not state of the art 2M DX gear, also there are some very VERY big FM broadcast alias images in the 2M band unless I use the LNA with its sharp helical filters. I am 51km from the BC transmitter.

Useful backup maybe if I lose/forget the Kuhne. Simple enough to add a linear with 0dBm input for 70MHz or 144 and an LNA, but I’ll keep the Kuhne thanks.

Compare result with the Kuhne. 15dB better C/N ration. All JT65/PI-RX tests in 2.4kHz bandwidth

005600 9 -5 1.1 -5 3 * GB3VHF JO01EH

From the FAQ: http://support.eladit.com/kb/faq.php?id=4

FDM-DUO 2m Operation
To unlock the DUO (up to 165MHz): low pass filter must be off, check menu #2 “RX LP” and output must be set to 0dbm in menu #33 “TX OUT”
output is on the 0dbm sma socket
to unlock SW-2 open FDMSW2SwSetup.xml with an editor and search for UnlockDUOt at the bottom of the file. Set it to 1.
RX antenna jack can be used for VHF antenna (so HF ant on RX/TX and VHF on RX can be connected at the same time)
external preselector needed & amp if you need more than 0dbm output (this is 1mW).

Noise floor and MDS tests of Elad FDM-DUO

Been doing some tests of my Elad FDM-DUO on HF bands with my noise-ridden lab environment.  Using my HP E4421B sig gen with 30dB screened attenuator, the minimum discernable signal using PI-RX and JT4A is:
472: -150dBm
1820: -150dBm
3503: -148dBm
5379: -149dBm
7010: -150dBm
10102: -149dBm
14002: -147dBm
18080: -146dBm
21005: -147dBm
24900: -144dBm
28005: -144dBm
28200: -145dBm
28500: -142dBm
29500: -144dBm
50200: -144dBm

I was wondering if I was getting noise from the local environment up the coax outer or power/control leads, but those measurements were made with the coax screen of the HF antenna connected to the radio, so I guess not.

With the antennas connected (at 2200utc), I see a noise floor of -142dBm on 28MHz, only a couple of dB more than with a dummy load. On 18MHz, about the same. Across the bands from 18MHz to 30MHz, I see a few tones and squiggles, worst tones about -120dBm. Looks like I don’t have any significant local noise, at least between 18MHz and 30MHz. Interesting. Bit different on LF and VHF, where I have some work to do!

As ever, this was MY Duo and MY lab, YMMV!