Messages

31

Equipment / Re: BELKA DX

« on: July 15, 2021, 1602 UTC »

Great - thank you.

I may have to borrow the other laptop for this - the cheap laptop at the radio desk is running from a plug-in USB sound I/O that I now realise only has mono input.

Further, I'd like to explore going really mobile with Belka and a spectrum analyser to check out HiFERs from other locations. A brief test with the laptop and the Belka receiving with the whip resulted in 5&9 reports to the computer, traced to the screen. Second test was to try a small tuned loop. Care with the feed decoupled most of the QRM from the PC. I think this had promise, but for the test, conditions were just awful.

Ed

32

Equipment / Re: BELKA DX

« on: July 14, 2021, 2032 UTC »

Thanks for the insight here SIGINT

So far, a quick test using just the headphone output - mimicking the same methods used with the conventional receivers. However, additional bandwidth would be a great benefit, particularly for monitoring 22m beacons. Since the whole band is only 14 kHz wide it could be monitored at once even with the basic audio facilities in the PC on my radio desk. I have yet to play with I/Q techniques, but plan to explore eventually.

33

Equipment / Re: BELKA DX

« on: July 13, 2021, 2000 UTC »

Jumping in a bit late here - I acquired a Belka DX a couple of months ago and have been extremely impressed with this little receiver. It has seen use with headphones and ear-buds and provides plenty of audio with either. For antennas, the whip is excellent if true portabity is needed, but the radio seems to work nicely with my external antennas.

I do a lot of monitoring for 22 m beacons, and put Belka to work, feeding the audio to a computer running Spectrum Lab. For this operation, it was a serious rival for any of the table-top receivers, and was excellent on this weak signal work.

For broadcast, the "pseudo-Sync" is very well implemented, and the recovered audio is very clear. It almost pains me to say it, but it's ability to "hang on" to a signal and maintain clarity perhaps exceeds the very good AMS of the Lowe HF-150 and HF-225

Before purchase, I had wondered if the minimalist controls could be difficult, but they are very easy to learn and use. It has a smooth and professional feel.

Count me very pleased to own this radio.

34

The RF Workbench / Re: Inexpensive frequency counter Modules

« on: September 09, 2020, 2117 UTC »

Thanks again for all replies.

For bench duties, I recently sourced a decent used counter from a popular auction site. It has a temperature stabilised reference, and gives trustworthy results. Listening to the 10 MHz reference against WWVB on a receiver, it is rock solid and within a Hertz or so after warm-up.

Cheers

Ed

35

Equipment / Re: To Chuff or not to Chuff?

« on: September 09, 2020, 1947 UTC »

On my variant of this model, I included a switch so that the chuff/no chuff could be turned on or off. A small slide switch was mounted discretely on the side of the case. The noises heard with anti-chuff mod implemented are to do with the native 1 kHz base frequency at which the PLL circuit operates. It generates a lot of phase noise as one makes frequency steps, until the PLL lock stabilises again. IIRC it is not so noticeable on quiet bands, but acute when tuning on strong signals.

The whine, I remember well enough. I seem to remember curing it with better shielding between the CPU/controller board and the ferrite rod antenna. It was a long time ago since I made that mod, so details are a bit sketchy, but it did involve digging quite deep in to the radio, removing the RF board.

Once, just once I was able to get the set to do something weird and neat that I have since seen reported elsewhere. With some odd combination of battery change and application of power, it forgot it's tuning limits, and let me tune long-wave below 150 kHz, all the way to zero on the dial. Whether this was any use or not, I don't know, but it was cool at the time.

36

Equipment / Re: Equipment needed for beacons

« on: September 09, 2020, 1849 UTC »

When I picked my call, it was both an oblique reference to location, and to the construction materials (PVC) used to build the antenna.

It also makes sense to choose an ident that is easy(er) to read as a weak signal. This involves care in the choice of letters to get a sensible ratio and juxtaposition of dots and dashes. For example HI would be a pretty poor choice (.... ..) ,  whereas XO (-..- ---) might work quite well, if one is using simple keyed CW. For FSK, things are a bit easier, because the carrier is always on.

Choosing a frequency has a number of aspects. The first is doing one's best to stay away from the centre of the band at 13,560 kHz. There is a lot of commercial interference here, so it is much harder for a mW power beacon to be heard in the QRM. The second factor is the adjustment range available with the setup, especially if trying to "pull" a crystal oscillator. This could determine whether the transmitter is above or below the band centre. Lastly, of course, it is polite not to land on top of another beacon, but one can afford to think really narrow, and 100 Hz, perhaps less, is a decent margin. Listening is often via spectrum analyser, so as long as traces don't overlap, they can be picked out. There are a couple of beacons that are well known for drifting up and down in frequency as the local temperature changes. There are no hard and fast rules, aside from working within the band limits, and not exceeding the maximum allowable field strength, but there are some good tactics to enhance one's chance of getting some reports.

Cheers

Ed

37

The RF Workbench / Re: Inexpensive frequency counter Modules

« on: August 28, 2020, 1458 UTC »

If not the same, it looks very close. Thanks for the tip. I'll have to scare up some instructions, but I'll be interested to see if accuracy can be improved.

38

The RF Workbench / Inexpensive frequency counter Modules

« on: August 25, 2020, 2358 UTC »

Hi Folks,

I am sure  a few of you have seen the inexpensive frequency counters available on-line. I bought a couple out of curiosity, featuring an 8 digit LED display. They are quite useful, e.g. for adding to an old signal generator, but beware using them for more precise work.

A case in point - I acquired a Yaesu FRG8800 a couple of years ago, and decided it could benefit from a tune-up. I used one of the counter modules in the course of this, and alignment generally seemed to go OK. Except there was a constant offset either USB and LSB modes, around 300 Hz. That seemed odd, but since the radio was in spec according to book values, and the small error could be corrected with the "Fine" tuning control, I didn't think much of it, and put it down to drift during warm up etc. Recently, I had another reason to bring the set back to the bench, and since I now have a better frequency counter, decided to look at alignment again. Lo and behold, the local oscillator settings for both USB and LSB final detection were incorrect by practically the same amount, and consistent with the error in tuning the radio. Using the new counter, and following the alignment procedure again has put the radio spot on frequency. Lesson learned!

Cheers

Ed

39

22 Meter Band HiFER Beacons / Re: LBC 13559.93 KHz 03AUG2020

« on: August 11, 2020, 2147 UTC »

Hi DYGradio,

I can confirm LBC, which popped up just before Mid-Day on 19th July, strongly audible here in California amongst the usual ~13560 kHz signals. It has also been reported by other listeners over at the LCWA site. Its origin is a mystery so far.

Ed

40

22 Meter Band HiFER Beacons / Re: Some Grabs from Sweden / grabber online

« on: April 08, 2020, 0344 UTC »

Very impressive. Thank you for sharing

/Ed

41

22 Meter Band HiFER Beacons / Beacon PVC running QRSS3

« on: April 08, 2020, 0341 UTC »

As the thread title says, I have adjusted beacon PVC to QRSS3 mode, sending the ident PVC. Frequency is unchanged at 13,555.55~

Cheers

Ed

42

22 Meter Band HiFER Beacons / Re: Using a 20m Yagi for reception

« on: February 24, 2020, 1125 UTC »

The most important thing I have found for receiving antennas and in particular for weak signal work is to guard against common mode noise. I am not sure how a Yagi will behave so far away from its design frequency, but would expect it to be rather inefficient, and with quite unknown directional response. However, if you can be sure that noise on the outside of the coax feeder doesn't add to the signals picked up by the elements (use of a good balun etc.) then the antenna could do well enough if also away from local noise. Since it is there, you might as well try it!

One of my receiving antennas is a "random wire dipole" made to fit the available space, with about 45 ft on each leg. At the centre connection to the coax I used a home made balun with separate primary and secondary windings, built on a binocular ferrite core. I think the transformer is an important part of the success of the system. Common mode noise on the coax is horrendous, but is completely absent in normal use and the system is great for 22m beacon reception. I have a long wire also connected in a similar manner, using an isolation transformer between aerial and earth points at the antenna, and the signal and shield of the coax. Similarly, this also does well in keeping the house noise out of the radios.

Cheers

Ed

43

22 Meter Band HiFER Beacons / Re: 22m Beacon

« on: January 21, 2020, 1826 UTC »

Sounds like you are on the right track IZS4

I have experimented with a couple of antennas, starting out with a 1/4 wave vertical plus radials, then (and most successfully in terms of reports) an inverted V type dipole. Both setups were mounted on the house roof.

Cheers

Ed

44

22 Meter Band HiFER Beacons / Re: 22m Beacon

« on: January 10, 2020, 2032 UTC »

As Chris stated, the regulation is based on field strength. That equates, IIRC to about 2 mW into a vertical, or 4 mW into a dipole. Of course, what you are able to put up for an antenna will have some bearing, as will the local environment, on losses. But there's no point, obviously, in an antenna with gain. For a beacon, you want relatively uniform radiation in all directions anyway, to maximise the chance of reception.

The restrictions are pretty tight, but that is what seems to make HiFERs fun to many of us who operate and listen at 22 m.

Cheers

Ed

45

22 Meter Band HiFER Beacons / Re: Beacon PVC temporarily off

« on: December 15, 2019, 1906 UTC »

PVC restored 

I found a broken wire at the mast head balun. The system must have taken a real beating in the storms. Also had to repair/replace the guy wires. Now opearating at the usual signal strength, as verified from a nearby receive antenna.

Cheers

Ed