HFU HF Underground
Loggings => 22 Meter Band HiFER Beacons => Topic started by: Ed H on September 05, 2018, 1940 UTC
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Hi Folks,
It occurred to me that it would be a good idea to share the quietest listening spots in the 13553-13567 ISM allocation we know and love as the HiFER band.
My reasoning for this is more or less obvious - Where is a good spot to put one's beacon, if trying to reach a particular area?
For my QTH in the SF bay area, the only spot with consistent interference is 13560 - 13562 (as tuned in USB with a typical 2.2 kHz filter). Ergo, I can easily listen from the lower portion of the band, up to about 13,559 before whistles and bleeps interfere with hearing, or the AGC kicks into action. Using a Spectrum Lab, this can be pushed a little further. On the high side, 13,562 kHz up is all quiet.
I would be interested to hear from other beaconeers on their local conditions.
Cheers
Ed
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ISM band (HiFer) : 13553 kHz to 13567 kHz
There is much less interference in the 3 kHz windows near the edges at the bottom and top:
13553.2 kHz to 13556.2 kHz is good.
13563.8 kHz to 13566.8 kHz is good.
The centre of the band at 13560 kHz +/- 3 kHz has by far the most interference:
13557 kHz to 13563 kHz is statistically the worst.
13.56 MHz is one of the most common laboratory, medical, and industrial plasma frequencies. The centre frequency, 13560 kHz, is populated worldwide by thousands of kiloWatt-level transmitters for MRI, NMR, semiconductor plasma ion deposition and sputtering chambers, industrial plasma, plasma arc, etc.
Luckily, most of those high power devices are within RF shield rooms or shielded chambers. But, even a little bit of leakage from a kiloWatt device in a screen room could easily compete with Part 15 HiFer beacons, especially when the propagation is favorable.
RFIDs on 13.56 MHz don't usually cause much interference.
A quick survey of 13560 kHz on some of the better SNR remote SDRs provides an easy way to check the HiFer interference landscape.
(http://hfpack.com/members/exo/ISM_Band_13560kHz_Interference_Temperature_Zones.jpg)
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I will at some point move my transmitter to a different frequency, but as of right now I am at 13.561.6. I do hear the qrm at 560-561 at my end but from 553 to 559.3 and 561.5 to about 566 ia usually pretty good for me when listening on both my 80m ocf and 30 m dipoles!
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I would expect the band centre to have the most issues... Equipment using this frequency is likely crystal controlled, and 13.56 crystals are likely to be relatively well clustered around centre.
I'm considering moving my beacon frequency, but need to implement a different frequency source than the crystal which has limited pull range. It's worth figuring out what the better spots will be in the band.
Using web SDR is a great idea to do some surveying myself. Not so many of the ones I have found provide full HF coverage, but a few allow reception of 22 m.
Thanks
Ed
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I'm curious if the band has just not been behaving well or if I truly am not getting out as well as I had hoped?
20 meters hasn't been great for me lately either, so I suppose my beacon probably is just fighting conditions as they are?
Which SDR do you recommend for 22 meters, Ed?
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Generally the only interference I get is centered on 13560, there's a repetitive pulsing signal there. It's only a problem within roughly a 1 kHz region.
22 and 20 meter reception has been poor here the last week or two. I've not heard any beacons, and while I run my SSTV decoding app 24 hrs on 14230, there's been far less received than earlier.
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Thanks again for the feedback everyone.
Exo - your pic did not appear the first time I came back to the thread, but that is a great illustration, and very similar to what I experience along with others.
I also posted this at the LWCA message board, and I'll share what comes back.
Cheers,
Ed
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How far has one been able to pull a Black Cat 22m beacon (and how?)
I've been able to pull it up slightly, but it seems as to be expected the addition of caps brings the freq down into the QRM zone.
Perhaps a thread for another discussion but found it fitted in some way / context.
The Ultimate 3 I have is obviously not an issue, but as previously mentioned in this thread, crystal controlled devices seem to be clustered.
Would be interesting to hear other thoughts on this
Jason AKA TickingMind
Beacon J1LPB
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You are welcome to discuss the frequency pulling question on this thread. It is all connected :)
I moved PVC to a new temporary frequency using the generator. It is a simple switch press on the transmitter to go back to the crystal at 13,558.4 kHz
Prizes for correct answers to "What frequency is PVC on today"
Cheers
Ed
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You are welcome to discuss the frequency pulling question on this thread. It is all connected :)
I moved PVC to a new temporary frequency using the generator. It is a simple switch press on the transmitter to go back to the crystal at 13,558.4 kHz
Prizes for correct answers to "What frequency is PVC on today"
Cheers
Ed
Very weak but I started to hear some chirps on 13,563.760. Never noticed them before, a little too weak to make anything out (yet) but keeping the decoder on it when not watching. Maybe it's you???? ;)
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Thanks for the report. However, this is not the present frequency for PVC. Keep trying :)
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I live 5 miles (8km) north of the northern border of Ohare airport. Just west of Ohare is a large area of several square miles of low rise commercial and industrial buildings. There is a constant 24/7/365 assortment of weak signals around 13560 from that area. If I remember correctly they are there even on xmas and new years. If MRI's also use that freq there is a big hospital complex with an MRI in the basement about 3 miles west of me. I was in that MRI once back in 2009 (long story).
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More activity on 22m from ISM soon at 10 kW in Costa Rica:
http://amfone.net/Amforum/index.php?topic=44225.0
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Perhaps time to investigate the rest of the ism bands.
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If you examine the way-cool waterfall SDR screen-grabs Exo made above of the 22m ISM band, there seems to be at least two broad (hash/hiss) bands between 13560 and 13562 kHz, this is heard globally and is almost "always there" when there is even some prop. on 22m, even if it just riding the MUF.
Does anyone know what creates this global hash/hiss band(s)? It seems to be a complex "mash" of discrete A0 carriers all co-mingling.
I very much concur with the band-research and findings above. I op'd. two hifers on 22m (legal!) in 2014 for a spell (unreported in DX press "RR-dash" and "VAN" - the latter in an old Ford van with an inside its fibreglass top roof and hrd. by John Davis of LWCA fame in KS!) ...
However, I became tired of the "crud-scape" in this band and gave-up for quieter s/n bands. But keeping to the lower/upper edges of this ISM band indeed there is good reason to do so, what with the waterfall displays above showing the very obvious.
Unless you can find a channel-13 xtal (3x overtone) or rarer a fundamental CB xtal for div. by 2 op., it can be hard to avoid 13562 etc. (unless one has a good PLL system on the xmtr. osc. to xmit. on the lower/upper edges of the band that is in-the-clear).
I might re-activate my 2m beacon someplace remote so its QRM does not mess-up my listening... 73-MB
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BTW, in China in Nov. 2013 I noted ISM Crud all over the 11-m CB band along with lots of CB AM-mode skip from Japan (ch 4 27.005 esp.) and AM/FM from Malaysia on CB-19-27.185 etc. (and pirates elsewhere filling the band.) More than I ever heard in the states! Sweepers, pulsars and the usual 22m crud was all over 27 MHz also there (not surprising considering the density of population and industry in east Asia, etc.)... (MB)
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ops correction: 13560, 13562 kHz rather than incorrect 13360/13362 (sri!) MB
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That noise region certainly checks out here in Northern Calilfornia. I should bring a receiver to work - we have lots of tools with RF generators, I'll bet the ISM is a riot here in San Jose!
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If you examine the way-cool waterfall SDR screen-grabs Exo made above of the 22m ISM band, there seems to be at least two broad (hash/hiss) bands between 13560 and 13562 kHz, this is heard globally and is almost "always there" when there is even some prop. on 22m, even if it just riding the MUF.
Does anyone know what creates this global hash/hiss band(s)? It seems to be a complex "mash" of discrete A0 carriers all co-mingling.
Just guessing, these 1-to-3 kHz wide noise "hiss" signals seen around 13.56 MHz ISM are possibly due to the use of "Low EMI SSC" techniques in some of the ISM generator transmitter designs.
SSC is so-called Spread Spectrum Clock oscillators, which have an intentionally frequency-dithered output.
(Not really spread spectrum as in SS communications)
In other words, the SSC is a clock oscillator that is frequency modulated with either a triangle wave or low pass filtered pseudo white noise.
This provides the same working power output for the generator, but legally fools the EMI testing standards into measuring an apparently lower signal strength level.
The EMI testing uses audio bandwidth time-weighted level measurements.
It also gives the ISM signal the appearance and sound of noise hiss on communication receivers.
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That is an interesting supposition Exo.
Since I work at a manufacturing facility that uses RF generators, I could ask. It is also a perfect excuse to bring the portable listening setup to work :)
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Last week I brought the Lowe HF150 in to the office. It has a sensitive Hi Z active antenna input. Alongside a few carriers within ISM limits, was a massive broad-band hash from all the other equipment and lighting circuits. In fact this was plenty audible with the whip antenna switched to the straight 50 ohm input. I didn't get chance to monitor from outside the building.
One last thing - There was a nice clear dasher signal.. traced to the NFC/RFID transponder of my smart-phone!