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Messages - Ed H

Pages: 1 2 [3] 4 5 6 7 8 9
31
22 Meter Band HiFER Beacons / Re: FJB
« on: December 06, 2021, 2310 UTC »
FJB was copied by ear on Dec 4th, on the S.F. Peninsula. Good clear signal, just above the noise

32
Equipment / Re: Can a common mode choke really help reduce RFI?
« on: December 02, 2021, 1843 UTC »
Nice illustration of the improvement Chris.

In tinkering around with reception of LowFER beacons and 630 m activity, I have found similar measures very helpful. The outdoor long-wire is transformer coupled at the feed-point, which also has a ground rod. Only the antenna side winding of the transformer is connected to the rod. The winding connected to the coax is "floating"

At the receiver end, I have another isolating transformer that can be inserted into the feeder. Not exactly a CM choke as such, but the intention is the same, add a high impedance for common modes. It seems to help a lot.

Touching the shield of the incoming coax to the centre conductor of the radio provides a very convincing demonstration that these measures are effective.

Ed

33
Equipment / Re: BELKA DX
« on: August 17, 2021, 1803 UTC »
Interesting results, thanks for sharing. I've had no opportunity for testing (distracted by other projects) but will follow up. One requirement is a stereo mic or line input to the PC - I don't have anything to hand yet.

34
22 Meter Band HiFER Beacons / August 15th WSPR
« on: August 17, 2021, 1758 UTC »
Here in Northern California, WSPR signals from EDJ, SIW and SZX were recorded during 22m monitoring, daylight hours, 15th August. Other Beacons noted were 7P, EH and NC from traces recorded in Spectrum Lab. EH is occasionally audible here, as is 7P.

Receiving with random wire dipole and Icom IC R-72

35
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

36
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.


37
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.

38
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

39
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.

40
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

41
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.

42
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

43
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

44
Very impressive. Thank you for sharing :)

/Ed

45
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

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