Re: Lowest cost LF receiver
Posted by Eric KD5UWL on August 01, 2004 at 21:03:43
If you have an HF rig, how about this:
http://www.cpinternet.com/~lyle/proto/LFproto.htm#LFconv
73
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 01, 2004 at 23:18:23
Yes.
The Mac G5 is a reality up to 8GB of ram and "Pandaa" a student in Sweden modified his mac "Frequency" spectrum analyzer to work up to 33 million 24 bit sample FFT's.
My radiating loop setup is mainly there to produce a signal to test the software under real conditions. But I have found that there is radiated power and I have to source feed only 1mW of power to easily detect a large signal from 30 feet.
Of all of the signals I've heard of below 22kHz, they all would appear as straight or slightly trending lines when using large sample FFT's and not really distinguishable from a large number of 60Hz harmonics and 60Hz correlated non-random traces. Hence the need to source 1000+ second on and off signals.
Antenna Book
Posted by Charles Weaver on August 02, 2004 at 14:14:08
I want to purchase a 1992 to 1994 ARRL Antenna Handbook but do not want to pay the $40.00 for new. Anyone out there that has an extra or several year old version they would be willing to give up?
Thank You
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 02, 2004 at 16:02:26
Hi John,
I was thinking about the tone of your response to my posting. Any feed back is welcome when one is involved in a lonely pursuit.
The reduction of bandwidth is a standard radio engineer's technique to deal with weak signals. JPL will reduce their space probe data rates to as low as 10 bits per second when faced with weak signals. I have only taken that technique to the extreme. There is no serious opposition that increasing the frequency resolution increases the signal to noise ratio, directly, compared to a precise and stable sine wave signal.
Dave Rickett
Re: Lowest cost LF receiver
Posted by mike miller on August 02, 2004 at 19:50:04
How about fair radio sales company ? (fairradio.com)
All sorts of vlf receivers.
Re: VLF Low Bit Rate DSP
Posted by Alan G3NYK on August 05, 2004 at 18:19:46
Hi Dave, up a bit higher in frequency work has been done down to 120 / 360 second elements. My own experiences probably like John's are more up in the 136kHz region, but the basic problem of signal in noise is the same. I have found in trawling for weak signals that it is possible to come across all sorts of artifacts, that look as though they may be a signal. They may even go on and off, the one thing they do not possess is frequency shift keying. I have suggested to those running weak beacons that a periodic very small frequency shift is a good way of identifing a weak signal. Ideally also you need to know where to look with some high degree of accuracy. Some work has been done at 136 kHz with GPS locked timing, with fair success, but few are equiped at this level. There is some interest in sub 10khz in the UK but our licencing authority wields control even down there, and we have not been successful yet. The only experiments I know of have been in Germany, I believe under a special permit, see Geri DK8KW's site.
Regards Alan
Re: Radio Caroline could be revived
Posted by Mike E Terry on August 08, 2004 at 13:48:45
Hi Fred,
Hope you had a great time on the Ross, email me off list if you like.
Mike A Caroline listener for 40 years!
Needing receiver advice
Posted by Gary on August 08, 2004 at 19:11:51
Hello,
I've been browsing on eBay and several radios have caught my eye:
A 1) Degen 1103 and a 2) Realistic DX 302.
From what I've read they both have their short-comings (what doesn't?) but seem to be adequate receivers for their price.
Does anyone out there have any experience with, or comments about, either of these radios?
Thanks!
- Gary
Re: Needing receiver advice
Posted by John Andrews on August 09, 2004 at 08:44:18
Gary,
Where are you located, and what would you be trying to listen to on one of these radios?
John Andrews
Re: Needing receiver advice
Posted by Gary on August 09, 2004 at 12:35:47
John,
I live in Rochester MN and am primarily interested in NDBs. I have a Grindig Yachtboy 400PE, but that only covers the LW broadcast band. I'm able to pick up a number of beacons, but want to heard more of what might be out there.
Thanks,
- Gary
Re: Needing receiver advice
Posted by John Andrews on August 10, 2004 at 14:40:17
Gary,
OK. I've been hoping someone with more knowledge of those two receivers would jump in here, but nothing heard. So let me give some background, and we'll see if anyone can help with the specific equipment.
A lot of radios will work well for NDB chasing, but you'll quickly find out that the antenna is very important. Radios with internal antennas are better suited for broadcast reception in Europe, where the LW stations run hundreds of KW. You will greatly prefer a receiver with a decent external antenna.
If you have an HF receiver, an LF converter ahead of it would be an excellent choice. If that's not available, a communications receiver is the best approach. Such receivers are usually "deaf as a post" at LF when connected to 30 feet of wire. But it's easy to add a preamp or use a better antenna at these frequencies. You might have some problems with local AM broadcast signals, but among your antenna choices are ones that are tuned pretty sharply, thereby reducing the broadcast clutter.
Most NDB reception is done with the receiver in CW or SSB mode, rather than AM. Selectivity can be an issue for serious work.
Wire antennas, particularly ones tuned against ground, are a typical starting point. A good e-field probe antenna mounted up in the clear, can give excellent results. Loop antennas, ranging from the very small to very large, are used for a lot of the weak signal work.
I'm not really an NDB chaser, but a couple of years ago I was able to log 63 NDB's in the early afternoon on a summer day. The nighttime possibilities are endless. My LF receiver is an Icom R75, which I can heartily recommend for general use.
John Andrews
FWD: L.F. Test 15 th August 2004
Posted by John Davis on August 10, 2004 at 20:58:34
Subj: LF: L.F. Test 15 th August 2004 Date: 8/10/04 6:13:57 PM Eastern Daylight Time From: andrewss@earthlight.co.nz (Stan Andrews)
To: rsgb_lf_group@blacksheep.org
Hello All,
Robert, VK7ZAL, Hobart,Tasmania, Australia, advises that he will be running his beacon transmissions on Sunday 15th August over the time span of 6 P.M. to 10.00 P.M. Tasmanian time.
Frequency 177.5 kc/s LSB
Any reports of reception to Richard VK7RO at vk7ro@netspace.net.au or myself, Stan andrewss@earthlight.co.nz
Robert also advises that the snow line is rather low on Mt Wellington so there is no prospect of transmissions at the moment.
We also have a little snow here in Dunedin on Mt. Cargill
73,
Stan ZL4MB
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 11, 2004 at 14:20:23
Thanks,
I speculated about both on and off as well as small frequency shifting during the first postings about a year ago.
In the US our FCC stops allocating frequencies at 9kHz. My favorite frequency is 8999.000Hz (8999 is a prime number). It skirts 9000.000Hz which has artifacts from 60Hz electric power and equipment noise correlated to 60Hz.
Do you use a fine resolution spectrum or time-frequency analyzer for 360 second elements? For Mac users the software I have is ok but I have heard of no MS OS shareware that is good for 8999.00 or 8999.000 Hz. Expanding high resolution spectrum analyzers to the PC world would greatly expand the group of people who might be interested in detecting weak VLF signals
I will check out Geri DK8KW's site.
Best regards,
Dave Rickett
Re: VLF Low Bit Rate DSP
Posted by Alan G3NYK on August 11, 2004 at 16:54:03
Hi Dave, All (or most) of the work a 136 has been done using either Alberto's (& associate) ARGO or Wolf's Spectrum Lab. The BPSK work was done by Bill deCarle, who also has looked at GPS synched DFCW (dual frequency CW)which is easy to generate with a DDS. All of this s/w is PC based (Win95 and above) Alberto is "playing with" GPS synch, as a retirement project....but you know how other jobs get in the way then !! I think he has a target of GPS synched JASON which is a multi-frequency keyboard mode. One requirement for ease of transmission at 136 has been that the mode is compatible with non-linear PA stages, which most stations use.
Regards Alan G3NYK
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 13, 2004 at 17:38:02
Hi John,
Your posting response is interesting but I cann't tell what you are talking about. I use acronyms to refer to commonly known terms. Like DSP to refer to digital signal processing as opposed to analog reception which would be hard pressed to resolve a signal to less than 50Hz. I also use VLF to refer to very low frequency for 3 to 30 kHz. But I have no idea what the relevance of GPS is to low bit rate DSP. GPS to me is global positioning satelites. DFCW means nothing to me but at least you defined it in english and DDS means nothing to me. Dual frequency signals are easy to generate with any fairly new digitally controlled signal generator or software controlled computer signal generator. I remember when some people were obscuring what they were doing with 10 bit per second phase sifting but were really using illegal power and antenna length.
The significance and simplicity of my work is large(currently up to 2^25 sample FFT's(fast Fourier transforms) in spectrum and time-frequency personal computer applications. Does Spectrum Lab or any other MS OS(microsoft operating system) use more than a few thousand samples per FFT?
Dave Rickett
6 Hifers received in The Netherlands
Posted by Peter Knol on August 15, 2004 at 04:32:12
Hello Beacon DXers,
A HiFer RX report of last night (Aug.14/15) is published on http://home.wanadoo.nl/cyberknol/hifer/
Pse let me know if you like me to monitor for your HiFer.
Just send me the frequency as close as possible + mode.
I did monitor between 13.554,960 and 13.555,480 for the last couple of day's. I did copy LP,GA,GG,VD,MP and WA.
73 es gd DX, Peter PA1SDB in JO33KH / The Netherlands...
Hifers received in Norway
Posted by LA5VNA Steinar on August 15, 2004 at 07:02:41
Hi Peter,
The HIFER beacons was also captured in Norway last night. I was using a new antenna. It is a sloping half-wavelength dipole and it seem to be working really fine :)
The picture is posted on http://www.aanesland.com
LA5VNA Steinar
Re: VLF Low Bit Rate DSP
Posted by Alan G3NYK on August 15, 2004 at 18:02:35
Hi agn Dave, Sorry about that...any topic tends to generate its own jargon, I had thought that maybe you had followed the trail on the Home page. To me DSP (and FFTs) is just a tool and doesnt mean anything either, mainly because I know what they do but am too lazy to write my own code. If it is used to anyalyse a band of RF and produce a display indicating the presence of signals, it can start to be used for communications.
ARGO, Spectran, and Spectrum Lab are programs using DSP to via the sound card in Windows on a PC to do this. The common display is in the form of a "waterfall".
ARGO has the sample lengths optimised for the speed used, and easy to operate as part of a comms system. Spectrum Lab and Spectran are more flexible in that you set the sample speed and length. Spectrum Lab also contains a "library" of software configurable "radio" modules, and filters, together with decoders for BPSK and some other modes. As far as I am aware little of this sort of development has been done for the MAC, though there is some software for Linux.
DFCW stands for Dual Frequency CW am FSK visual mode where the "dots and dashes" of Morse code are the same length but are sent on slightly different frequencies.
GPS synchronisation allows a transmitter and receiver to run in synchronism....the receiver knowing where the bit transistions are due to the accurate timing. This allows anothe 3dB signal to noise to be achieved over unsynchronised modes.
I am not saying that these are the ideal for the things you are interested in but it would be worthwhile seeing what has been accomplished on the higher frequencies. Some ideas may be applicable some may not.
A lot of this is covered on Rik Strobbe's web site www.qsl.net/on7yd/136khz.htm I think its the digital modes pages.
I hope that make things a bit less murky..
Cheers de Alan G3NYK
Re: VLF Low Bit Rate DSP
Posted by Lyle Koehler on August 16, 2004 at 10:21:35
To add to Alan's explanation of the "jargon", many experimenters are using direct digital synthesis (DDS) in combination with GPS-disciplined frequency references to generate signals at precisely known frequencies.
There is a practical limit to the use of DSP to achieve narrower and narrower bandwidths, because the time required to detect whether or not a signal is present is inversely proportional to the bandwidth. I believe that Spectrum Lab is capable of frequency resolutions on the order of 0.0000002 Hz, which would require dot lengths of several months for optimum detection in slow speed CW mode.
FWD: Change of provider for the weaksignals site
Posted by Webmaster on August 16, 2004 at 20:20:36
Subj: Change of provider for the weaksignals site Date: 8/16/04 8:08:26 PM EDT From: dibene@usa.net (Alberto di Bene)
To: lowfer@lwca.org, hifer@lwca.org
Hello all,
Due to the persisting problems with QSL.NET in terms of unavailability and response time better measured in geological eras, I have moved the weaksignals site to a different provider, located in Italy.
This provider is different from that I asked some of you to test a few weeks ago.
There should not be problems, I think to have moved everything correctly, but please alert me if something seems to be wrong.
The address is unchanged, it still is:
www.weaksignals.com
Thanks
73 Alberto I2PHD
P.S. There is the possibility that your proxy has cached some pages, so if you see attempts to fetch something from qsl.net, please hit the refresh button of your browser.
Hammarlund SP-600 VLF questions
Posted by Charlie, k3ICH on August 18, 2004 at 09:57:23
I have recently obtained a very nice Hammarlund SP-600 VLF receiver that seems to be working perfectly. It even has most of the original Hammarlund branded tubes which by the way, all check good.
My question is basically what is the value of this receiver? To be perfectly honest, I bought it thinking it was a standard HF SP-600 and was surprised when I got it home to find it is the VLF version. My enjoyment of the old "boatanchor" radios is in the restoration and clean-up, not necessarily in operating them. (with the exception of a few that were nostalgia hot-buttons from my early days in Ham Radio.)
I am also looking for a copy of the manual for this radio, but so far, no problems seem to exist that would require one, and I am familiar with the operation of the SP-600 in general.
Thanks, Charlie k3ICH Leesburg Virginia
Re: Hammarlund SP-600 VLF questions
Posted by John Andrews on August 18, 2004 at 14:19:03
Charlie,
The major "hobby" use of these radios is for chasing non-directional aero beacons. The receivers are also useful for copying 160-190 kHz "Lowfer" beacons that still send regular speed CW. They should also be stable enough for tuning in the RTTY and DGPS stuff in the 300 kHz area, though you would need some software to make much use of those signals.
The receiver's stability and calibration would not be adequate for much of the slow speed activity in the 160-190 and 135-138 kHz regions, however.
My boat anchor guy here at work says that the VLF version is in some demand on eBay, and prices usually run $300 - $400, depending on condition.
John Andrews, W1TAG
Re: 6 Hifers received in The Netherlands
Posted by Eric KD5UWL on August 18, 2004 at 21:35:33
Hi, Peter,
SURE -- I'd like you to listen for *my* HiFER ... it is running QRSS3, ID "UWL", and frequency ... well, the frequency is often near 13555.435 ... I'm told.
BTW, I am working on a HiFER solution that will be MUCH more stable, frequency agile, and multi-mode for next season.
Thanks for listening,
Eric
Illegal Longwave Emissions in the UK
Posted by Dave Rickett on August 19, 2004 at 15:21:15
Hi Alan G3NYK, et al,
I just got this email from ofcom:
"From: David Donachie Date: August 19, 2004 6:46:21 AM PDT To: daver73769@mac.com Cc: Tony Howarth Subject: Unlicensed Longwave Operation
Dear Dave,
In the UK, we do not have an equivalent regulation to the FCC's Part 15. All radio transmissions require a licence or specific licence exemption in UK Law. The relevant legislation is the Wireless Telegraphy Act 1949 available from www.hmso.gov.uk . Experimental testing can be carried out on a Non-Operational development licence. The application form can be downloaded from here : http://www.ofcom.org.uk/licensing_numbering/radiocomms/nonop_licensing/?a=87101
Regards,
Dave Donachie
Associate Engineer (Technology OPS-EL-ELIC)
Ofcom
2a Southwark Bridge Road
London SE1 9HA
Tel. 020 7981 3173
David.Donachie@ofcom.org.uk"
Does this email accurately reflect your understand of the UK law on unlicensed longwave radio emissions in the UK?
My interpretation is that there is no legal unlicensed radio emission at the longwave in the UK.
Dave Rickett
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 19, 2004 at 16:11:20
Hi Lyle,
Your postings in the past lead me believe you were a cut above technologically speaking.
I would salivate to be able to work at 0.0000002 Hz resolution. It took me a year and serious $ to get to 0.001 Hz resolution. Not only would I have to invest in an atomic clock and a super computer based on thousands of G5 Mac servers to get to 0.0000002 Hz resolution, but software development would need to be dealt with.
I have previously asked if anyone know about spectrum or time frequency analyzers that worked better than 1 or 0.1Hz with a negative response. I would be shocked if Spectrum Lab worked at 0.0000002Hz resolution.
Dave Rickett
Re: Illegal Longwave Emissions in the UK
Posted by Alan G3NYK on August 19, 2004 at 17:18:56
Hi Dave that is the Ofcom (ex RA) interpretaion of the Wireless Telegraphy Act 1949. Whether that is the law might be open to interpretation by the courts on a number of points. The govenment body in the UK wishes to regulate any communication using e/m radiation from DC to gamma-rays. The fact that spectrum below 10kHz is not allocated to a service internationally, does not mean it is not regulated. I suppose more so now because the might be licencing money in it. There are certainly no equivalents of the lowfer/medfer/hifer allocations in the UK, or, I believe, anywhere in Europe. The German Amateurs got spectial permission to operate on 8.999kHz. However near field broadcasting is allowed, called "induction loop" in the UK I believe....this is where it all get very fuzzy. They are also now allowing churches or religious bodies to broadcast services on the Citizens Band....that should be good for a laugh having learned many new words during a short period I listen on CB. This rather seems like "making it legal cos people are doing it", which is how CB started legally in the UK. If we follow that lead ............what frequency did you say you were listening on ?? (Only joking Mr Ofcom)
As I do a little work in LMR I have what I believe is a "development licence", but I have no intention of asking whether it is the "right one"
Cheers de Alan G3NYK
Re: VLF Low Bit Rate DSP
Posted by Dave Rickett on August 19, 2004 at 17:50:31
Hi Lyle,
A year ago when we last posted, we were talking about noise and how much it is. I have now detected noise at 8999 kHz to a resolution close to 0.001 Hz and general noise is a frequency density. Reducing the frequency band pass directly reduces the noise. The noise at 8999.00 Hz is directly reduced at 8999.000 Hz. No surprise but comforting to verify actually. This effect continues for each decade reduction in frequency resolution.
The information rate surely directly declines with each decade in frequency resolution, but I assert that the total information transfer for all the intentional human unlicensed radio emission in the longwave is nil. Therefore low bit rate emissions are significant.
Dave Rickett
Direction-Finding Radio Equipment
Posted by Gary on August 21, 2004 at 11:30:25
Hello,
While browsing on eBay I've found a number of direction finding radios which cover LW,MW, and at least part of the SW band. From what is written in the eBay descriptions and what I've found searching on Google these radios, though being analog, sound like they would be excellent for beacon, etc. DXing.
Does anyone have any experience with or opinions about direction finders?
Thanks,
- Gary
New experimental HiFer in the Netherlands.
Posted by Peter Knol on August 21, 2004 at 16:48:10
Hello Beacon DXers,
I just finished building my HiFer transmitter and I wonder if someone can see the signal already...
Frequency : 13.555,310 Mhz Modulation pattern : Sawtooth Shift : 10 Hz Sawtooth cycle speed : 11 seconds Antenna : 45cm (17 Inch)Magnetic Loop QTH Loc. : JO33 / The Netherlands / Europe
It is in a experimental setup but will run until future notice.
73, Peter PA1SDB
Re: Illegal Longwave Emissions in the UK
Posted by Dave Rickett on August 21, 2004 at 19:50:42
Hi Alan,
You are obviously well informed about UK wireless radio emission law.
I noted on "Geri's" web site that Germany was regulated below 9 kHz.
But if amateurs can operate at 8999 Hz in Germany, I have not detected any intentional trace there and not for lack of trying. My detector is based on a 10 gain acoustic guitar preamp ahead of a Radio Shack public address 20 W audio amplifier, with band pass and low pass analog filtering, then into a Mac G5 native a/d line audio input and then processed for 0.001 Hz resolution. Do you think that is enough gain and noise suppression to detect an amateur signal originating from Germany in Southern Califorinia, USA? The input to the computer is nearly saturated with noise.
Best regards,
Dave Rickett
Re: VLF Low Bit Rate DSP
Posted by John Andrews on August 21, 2004 at 21:52:29
Dave,
Take a look at this screen shot:
http://webpages.charter.net/w1tag/files/AQC-9.jpg
This was taken using the entry-level "Argo" program. Back in 2002, a number of U.K. amateurs had permission to transmit in the 72 kHz region (no longer the case, sadly). The screen shows an hour-long recording of G3AQC sending the letters "AQC" in dual-frequency CW mode. His dots and dashes were of equal length, but separated by 0.1 Hz. My receiver was tuned so that the audio output of the dashes was on 800.9 Hz, and the dots were on 800.8 Hz. This is a transatlantic reception, one of a few made that winter on 72 kHz, with a transmitter output power of 2 kw, as I recall.
This is the maximum resolution for Argo, but the Spectrum Lab program mentioned by Lyle should be able to spread 0.01 Hz or less over a similar screen height. I suggest you go to DL4YHF's site and download the docs for Spectrum Lab, and form your own conclusions. His site is:
http://www.qsl.net/dl4yhf/
John Andrews
Re: Illegal Longwave Emissions in the UK
Posted by alan G3NYK on August 23, 2004 at 18:28:28
Hi Dave, yes it pays to keep up with the "politics", I know too many of the the old RA men to embarass them.
I have just re-read Geri's and Markus pages. There is no indication of what dot-speed they were using. From that we could work out the band width. assuming that 3 sec dots were used that is a BW od 0.3Hz. A ball park estimate might suggest that the distance would increse by a decade for every reducion in bandwidth of a decade (questionable but a start)The best DX so far is 10km so 0.03 would yield 100km and 0.003 1000km. You might be looking at about 2-3000km at 0.001Hz (probably wildly optimistic....but that what they said when I suggested Trans-Atlantic 137kHz might just about be on in 2000) I dont reckon that enogh to hear Germany. The frequency stability would probably have to be 0.1mHz. I would look for a "partner" within about 500 to 1000km as a starter If you have a kilowatt or so of power if not considerably closer. As far as I am aware only a few tests have been done in Germany and they are certainly not permanently active.
Have fun there is probably lots to be learned about that part of the spectrum.
Alan
Re: VLF Low Bit Rate DSP
Posted by John Davis on August 23, 2004 at 20:37:21
>>> I have previously asked if anyone know about spectrum or time frequency analyzers that worked better than 1 or 0.1Hz with a negative response. I would be shocked if Spectrum Lab worked at 0.0000002Hz resolution. >>>
With practical hardware, it would not. As you surmise, it would require the precision of atomic standards to obtain the theoretical resolution. In addition, the total bandwidth on display would be an extremely tiny slice of spectrum too, unless one invested in massive processor power. Talk about diminishing returns...it would quickly become more practical to invest in additional transmit power. :-)
John
ts-2000 longwave reception??
Posted by H Joseph on August 25, 2004 at 11:15:02
Hello fellow longwave listeners...
Can anyone comment on the quality of the ts-2000 transceiver for listening below 100 khz??
Re: ts-2000 longwave reception??
Posted by John Andrews on August 25, 2004 at 13:15:03
I don't have any experience with this particular radio, but most similar rigs seem to do pretty well at LF. The only problem is deafness, but that can be cured with an external preamp or a bigger than normal antenna.
I guess the question is what you would be trying to copy between 30 and 100 kHz?
John Andrews, W1TAG
Update "New experimental HiFer in the Netherlands."
Posted by Peter Knol on August 25, 2004 at 15:39:50
Hello Beacon DXers,
I did some small modifications, but unfortunately the frequency of the HiFer beacon did drift up a bit. The new frequency is 13.555,380 Mhz. The modulation pattern looks like a Asymmetric Sawtooth with 8 Hz shift and 12 sec. cycle speed. The antenna is now a half wave Dipole, and power is 1.8 mW transmitter output.
Pattern generator: 555 timer Modulator: LM317 TX: Epson SG8002-DC-PHB GRID: JO33
73, Peter PA1SDB
A bonehead receiver question, I know...
Posted by WD0EGC, RJ on August 27, 2004 at 17:24:02
I suppose I could lose my ham radio license for asking such a bonehead question...
Assume you have two unremarkable single-transistor oscillators, unshielded, say within a foot of each other. One is oscillating at 500 kHz. One is oscillating at 501 kHz. The exact frequencies are not important, but there is a 1 kHz difference between them. They are throwing a few milliwatts of RF into the room.
You turn on an AM receiver in the same room, and tune it slowly from, say 450 kHz to 550 kHz. What will you hear, if anything, as you tune across 500 kHz?
I say that you will hear a 1 kHz pitch as you tune across 500 kHz. A friend, also a radio operator, says you will hear nothing.
I bow to the wisdom of the group. Who is right??
Thanks,
RJ
Re: A bonehead receiver question, I know...
Posted by Ray W2RS on August 27, 2004 at 17:44:14
RJ,
I too bow to the wisdom of the group, but this bonehead says that your example sure sounds like a 1 kHz heterodyne to me, just like we used to hear all the time on the AM phone bands, and still do around 3580 and 7290.
73,
Ray
Re: A bonehead receiver question, I know...
Posted by Ray W2RS on August 27, 2004 at 17:46:30
Oops, I wrote 3580, I meant 3880. I know I'm a bonehead, but why did I have to prove it?
73,
Ray
Re: A bonehead receiver question, I know...
Posted by John Andrews on August 27, 2004 at 19:11:03
RJ,
I'm with Ray on this one. Other examples can be heard on any CB channel, or on the AM broadcast band at night. The broadcast version occurs because the frequency tolerance between AM stations is +/- 20 Hz. You will hear various low frequency beats as a result.
The reason for the 1 kHz tone in your example is explained by what takes place at the detector in the receiver. Everything up to that point can be assumed to be linear, and there will be no interaction between the two signals, even in conversion stages that bring the signals down to the IF frequency. BUT, the AM detector in the receiver (probably a diode junction) is very non-linear, and has to be to do its job. It's output will contain terms proportional to the square of the two input signals. As a result, the familiar sum and difference frequencies will be there, along with some lower-level products. Since the output filtering for the detector only needs to pass audio frequencies, the sum will be squashed, and the difference will remain. In your example, that will be 1 khz.
John Andrews
Re: ts-2000 longwave reception??
Posted by H Joseph on August 29, 2004 at 01:32:25
Thanks for the reply. I'm interested in time stations mainly, but would look for anything else that may propagate my way this winter...
2th Update "New experimental HiFer in the Netherlands."
Posted by Peter Knol on August 29, 2004 at 11:05:22
Hello Beacon DXers,
I did adjust the frequency of my HiFer beacon a bit because over night the frequency was drifting over HiFer VD his frequency. Just in case you where listening, the modification did take place between +/- 13h30 and 14h30 UTC today.
The actual uptodate details since Sunday 14h30 UTC:
Frequency: 13.555,430 MHz ID: Asymmetric Sawtooth Pattern.
Shift: 8 Hz Cycle speed: 12 sec.
Power: 1,8 milli Watt Antenna: Hor.Dipole Pattern generator: 555 timer Modulator: LM317 TX: Epson SG8002-DC-PHB GRID: JO33 On air since: 25 Aug.2004 - 18h00 UTC Website: http://hifer-nl.8k.com
I have published a wiring diagram and some technical information about the transmitter and modulator.
The latest reports are also published on that site.
73, Peter PA1SDB
www.lwca.org
potrzebie