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I am looking for an EDM 10 or 100 FM stereo transmitter. It seems they are still not taking new orders,anyone have a used one they care to part with? Also looking for a decent board,at least 4 channels and stereo,must be solid state.
I am looking for an EDM 10 or 100 FM stereo transmitter. It seems they are still not taking new orders,anyone have a used one they care to part with? Also looking for a decent board,at least 4 channels and stereo,must be solid state.
I am new here,but old hand at microbroadcasting having begun in the 60’s. I currently have 1700,101.7 and 13.567 on the air 24/7 using Zara ver 1.4 and having a blast!
Total posts : 45366Hello,
Sorry I can’t help you on the EDM but I was curious about your history. You mentioned starting microbroadcasting in the 60’s. I started in 1959 with a KnightKit AM transmitter. What did you use back then? Any “war” stories to share?
Neil
Total posts : 45366Well,it all started out with the Boy Scouts Explorer post troop sponsored by the local AM-FM-TV station. We got to play broadcasting off air in their production studios,and occasionally on the air! We all built kits from Edmond Scientific(I think or something similar)and made our own home studios. There were 20 some odd stations on AM staggered around town split between two frequencies and tied together on a leased phone line(metallic pair)and we all took turns at it. Covered the whole town that way! We would syncronize our clocks and steal the network hourly news from the local station,it was pretty professional all around. I discovered that a tube type am radio made a dandy transmitter by coupling the output of the local oscillator to an antenna and feeding audio into its antenna connection. Crude but effective and probably more than legal output,but what could they do to a 14 year old kid??? Those were the days!!!! Regards,Lee
Total posts : 45366What circuit/transmitter are you using to transmit on shortwave?
Total posts : 45366Wilcom,
I don’t mean to hijack this thread but I do appreciate your story. I had my AM transmitter, but I discovered that link coupling a FM antenna to the local oscillator of a tube type FM receiver also got on the air. Modulation was easy…just feed the audio into the grid bias circuit. This probably gave as much AM as FM but it sounded really good at my cousin’s house 3 miles away. I didn’t pursue it since in the late 50’s very few people had FM receivers and I kind of thought this might not be legal. I lived near a major air force base and was told they monitor all kinds of frequencies and that I had better be careful so I quit FM.
Neil
Total posts : 45366[quote=am1670acr]What circuit/transmitter are you using to transmit on shortwave? [/quote]
Interested in this answer as well. 🙂
I was just reading on the Part 15 LW stuff too.
Total posts : 45366It is a 3 transistor crystal controlled circuit I built up from scratch. It uses a transformer as a modulator in the final stage. I still need to build a proper antenna for it,range is poor on the current hunk of wire. I think vertical polarization would work better for local coverage. The modulation isnt the best and Im going to work on that over the winter. I will make it available if I ever get all the issues fixed! First I wanted to get a PLL FM exciter as I am tired of chasing this old muddy sounding BA1404 tuneable around the band.
Regards,Lee
Total posts : 45366No problem Neil,glad to hear your stories too! Hey,Im here to have fun,share stories and ideas,build some neat stuff. Would re-live my childhood if possible! Lets GIT-ER-DONE!
Coming soon:massive parts list of items for sale. Thousands of variable caps,fixed caps,resistors,feed-thru caps and filters. Stay tuned….
Regards,Lee
Total posts : 45366I moved this over so more would see it – I’m interested in shortwave too :-]
Experimental broadcasting for a better tomorrow!
Total posts : 45366Thanks for the move!
I’m really interested in the LW band as well. It appears as though we can also broadcast there as well.
[quote] use of up to 1 watt of power and a 15 meter long antenna between 160 – 190 kilohertz, in the longwave bands[/quote]
Total posts : 45366For total and complete abuse,just try and use the 160-190khz band,YUK! It can be done but its a lot of work for very little return.Most of the activity there is CW or Digital narrow band modes to increase the s/n ratio as it is one noisy band! Some digital stations have gone over 1000 miles! Might make those guys real unhappy if you put a wide AM signal on there. I like the 13mhz shortwave band better,it allows a lot more power and a reasonable antenna.I am in the middle of prototyping a transmitter for such use and will share the results here when it is ready for release. Luckily,you can legally homebrew up to 5 transmitters without getting certification! Not so for a kit!!
On another note,looking at FCC legal transmitters and antennas,I wonder if there is a list of certified equipment available or will I need to wade thru cyberspace hoping to see them all? I have concluded that I will be real careful with the legal limits and stay within them the best I can. I have my FCC GROL and Amateur licenses to protect! Knowing what units are certified would help tremendously and should be posted on this site,IMHO……Regards,Lee
Total posts : 45366Very cool! What exactly is the allowed range in the 13MHz area?
Total posts : 45366Here is part of the info found on the Part 15 Radio Stations of North America website:
Shortwave or HF Part 15 Stations (13,553 – 13,567 kHz)
(HIFER) = Acronym for “High Frequency Experimental Radio”, basically the same thing as a LOWFER or MEDFER but at HF (see LF and MF Keys for more detailed explanations). “New” term coined by the LOWFER/MEDFER community to accommodate this “newly discovered” and rapidly-burgeoning field of experimentation.
HF Part 15 stations occupy a narrow slice of the 22 meter shortwave band in accordance with the provisions of 15.225, which specifies a field strength limit of 10,000 uV (10 mV) per meter at 30 meters from the antenna. In practice this works out to 1.8 mW transmitter output power into a 1/2 wave dipole, or 3 mW into an isotropic (0 dBi) radiator. While this power level may sound minuscule remember that by comparison, only a fraction (< 1%) of the power a 100 mW Part 15.219 AM transmitter feeds to its antenna is actually radiated by even the most 'efficient' 3 meter antenna; in fact, the amount radiated is roughly comparable what is permitted in this HF band, yet some impressive DX as well as local coverage has been achieved at MF. On this HF band, unlike Part 15 mediumwave, there is no limitation on the size or type of antenna, feedline or ground nor on power output of the transmitter, except with respect to whichever combination of antenna and power chosen is required to reach the legal limit of field strength without exceeding it (and recalling that any gain effect even if incidental, such as might result from proximity to a reflecting suface or object, would cause an increase in field strength in the direction of maximum reflection which must be taken into account). In any case while the power output allowed here is not tremendous, it is indeed enough to "work the world" based on Amateur Radio observations on similar frequencies and power levels, via the excellent ionospheric skip characteristics of the band. Local range depends of course on the receiver used, its antenna, the prevailing noise and interference levels, etc. but should be at least comparable to and probably significantly better than that of a mediumwave Part 15 station - unlike MF, at HF especially this high in frequency, there is essentially no significant groundwave component and thus a major source of path losses is removed - local propagation is via direct wave - and also the baseline atmospheric noise level is far lower here than at mediumwave. The other main requirement under this Rule subpart is a frequency stability of +/- 0.01% under supply voltage variations of 85 to 115% of normal at 20 C (68 F) and under temperature variations of from -20 to + 50 C (+4 to +122 F). This might tend to scare off some potential builders but it is actually only 100 ppm, which is easily achievable with any reasonably decent oscillator and power supply circuit design and good quality crystals which are readily available from a supplier such as JAN or Bomar. Another possible design example: a CB crystal for 27.120 MHz and a simple 74HCTxxx series frequency divider would give 13.56 MHz and whatever the stability of the crystal originally was, it would be doubled (drift halved) using this scheme. It is also probable that this rule really applies to commercial manufacturers seeking Type Acceptance and for the homebrewer the FCC would tolerate a lesser degree of accuracy. Canadian RSS-210 rules, Section 6.2.2 (e) permit operation in the same band but at slightly higher field strength, 15.5 mV/m at 30 m. Their frequency stability requirements are similar. Canada also has another license-free HF band not available in the USA; 6,765 - 6,795 kHz. Field strength and frequency limits are the same as those for 13,553 -13,567 kHz. For AM broadcasting use, assuming a standard 5 kHz max. audio frequency (10 kHz occupied bandwidth), there really is only one frequency which can be used in such a narrow band: 13,560 kHz (this leaves a 2 kHz guard band on top and likewise, on the bottom of the band as well). It is recommended, in the interest of allowing as many as possible to use the band, that those considering broadcasting here either (a) reach an equitable time-sharing or scheduling agreement with other stations to avoid mutual interference, if using AM, or (b) operate SSB (Single Sideband), which is used by many full-power HF broadcasters around the world and occupies much less bandwidth than AM does. Inasmuch as most shortwave receivers can "hear" SSB (have a BFO), this should not be a problem. Using less audio bandwidth on AM, when possible (for instance, 3.5 or 4 kHz instead of 5) can help reduce interference potential as well. Narrowband FM can also be used but unfortunately, many shortwave receivers likely to be owned by the public cannot "hear" this mode. NBFM might be better than AM though, due to less noise, for wireless studio-to-transmitter link (STL) use of this frequency range in feeding other Part 15 units on AM (MF) or FM bands (an idea originated by the author). To the author's knowledge, no commercial manufacturer currently sells Certified transmitters for this band; or not, at least, for hobbyists/broadcasters - so it's "homebrew heaven" for those so inclined. Here is a page with some schematics to get the experimenter started. One company, MaxNet, does offer lease of Certified NBFM transmitters for this range, at a HIGH cost, for STL/TTL use as part of a complete system of Part 15 FM's to be used along highways as sort of a commercial "TIS" setup. Contrary to what some folks have been (erroneously) told by FCC personnel not intimately familiar with Part 15 Rules, this band is not strictly for ISM (industrial, scientific, and medical) use only; the author, in consulting with contacts in the FCC who write these Rules has learned that broadcasting here is indeed permissible (there are no written provisions to the contrary). However, United Parcel Service is planning to use this spectrum for specific applications and being a Part 15 operation as well, sharing the band and acceptance of occasional interference will necessarily be the order of the day (let's hope UPS sees it that way!) Also, those electronic anti-theft tags (RFID) found on clothes, CDs and just about everything else in stores today operate here too; you may want to avoid transmitting on this band too close to your local Mall! The lack of experimental broadcast stations operating here is truly amazing, considering the relatively generous field strength allowance and great (world-wide!) propagation in this frequency range. This Part 15 band is available in the USA and Canada for use by people like us: hobbyists, low-power radio and broadcast enthusiasts, and experimenters; not many people in other countries are so lucky, and in the face of commercial pressures there increasingly is less and less spectrum available anywhere to the average RF experimenter - why not make good use of the band?
Total posts : 45366Thanks for the info! Other than using SSB it doesn’t sound to be of much use =(
Will montior on the SW radio and see if anything shows up.
Total posts : 45366From my experience as a Ham operator, I know you can be heard at great distances with little power when the time (propagation condition) is right.
I had a QRP (low power) transmitter, about 1/4 watt, known as The Tuna Tin Two. It was housed in a Tuna can and had two transistors, hence the name.
From Northeast Ohio I was able to make good contacts into Florida and Alabama. It operated in the 40 meter band (7 mHz) CW (Morse code.) Of course it’s easier to do on CW than voice.
The antenna was a horizontal half wave dipole, at 25 feet. The lead in was 100 feet of RG-59 (cheap) co-ax cable so if I got 75% of that 1/4 watt into the antenna I was lucky.
Although 1/4 watt into a dipole is a lot more than you’re allowed on the Part 15 13 mHz band, that 10,000 uV/m @ 30 m you are allowed could go a long way when the conditions are right.
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