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Hi All. I beleive i have a schematic of the REA AMMHF-1 Mod Monitor located here…
http://www.radioassociates.com
Hi All. I beleive i have a schematic of the REA AMMHF-1 Mod Monitor located here…
http://www.radioassociates.com
I was looking over on http://classeradio.com and lo and behold, all references to the am modulation monitor schematic has dissapeared and been replaced with a link to the REA mod monitor. now a lot of you may remember i posted a link to it sometime ago here. well i was going through my files here and found a saved copy of that webpage. what do you know it features a calibration generator and measures positive and negative modulation just like the REA does. now this uses a analog meter, but it would not take much to add a digital bargraph in place of the analog meters and place it in a fancy casing. here is a archive of the original page. http://web.archive.org/web/20030407214108/www.netway.com/~stevec/ham/mod_monitor.htm
Interesting thought, Eh???
Rev. Robert P. Chrysafis
Total posts : 45366I just spoke via email with someone who has confirmed that the REA is indeed based on that schematic that was located at class e radio. The REA is a Upgraded version. and the Class E Radio Site and REA site are owned and run by the same individual. The person i spoke to says that this is indeed a good monitor and i trust his judgement as he is a broadcast engineer for a local AM blow torch.
Thank You,
Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.orgModerator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree
Total posts : 45366Hi!
I am the person who designed the schematic to which you refer, although I don’t recall posting my circuit at that particular site 🙂 If you look at the circuit, you will see that it is many years old, and I no longer offer any support to folks who try to build it. The circuit, or earlier versions that I also designed have been posted on the Internet for almost 10 years. I publish a lot of technical material on the Internet, and encourage individuals to build their equipment.
The class E transmitter site is my site, and of course I did design the REA modulation monitor as well. This is well known (or hopefully it is !!!!) 🙂 I’ve been in both professional and amateur radio for most of my life, and this IS what I do 🙂 I’ve also designed broadcast transmitters for companies, as well as other pieces of equipment (audio processors, etc.). REA is looking at the possibility of coming out with a multi-band, asymmetrical audio processor / negative peak limiter / mixer in one unit. It’s still on the drafting board for now!
Ok, A few notes on the old circuit: Getting the circuit to work properly requires a reasonable degree of technical knowledge and experience. I finally had to stop publishing it. There are still a few old copies left out on the ‘net. What happened, is that people would attempt to get it going, and run into problems – mostly with accuracy – that required significant dialog. I just ran out of time trying to answer the emails and even phone calls !! 🙂 The dynamic accuracy (response to program material and peaks) was always in question. There are also some “renegade” copies of this circuit floating around which have questionable modifications. I don’t know where these came from, but they are out there. By the way, the circuit required about 10 volts of RF across a 50 ohm load. That’s around 2 watts of power. Not usable with a part 15 transmitter.
In case you’re interested, I have many circuits posted at the class E web site This site is dedicated to people who want to build their own transmitting equipment. These circuits have been reproduced many times, and in fact, I am coming out with a series of kits which will implement these circuits, to facilitate building.
But, to answer the original question: The old circuit is not the circuit used in the REA modulation monitor. The REA Modulation Monitor is designed for very high accuracy, necessary for a commercial broadcast station or other application where accuracy is needed. The REA monitor is also designed to be a peak reading device, so you know your true peak modulation. There is also a peak-hold. The old circuit was good enough for the purpose for which it was originally intended – as an indication, using analog instruments, for amateur transmitters, where most operators also have an oscilloscope in operation, looking at their modulation.
The new REA monitor is in response to folks who need to know their true peak modulation percentage, to a high degree of accuracy, and that would respond instantaneously to all audio peaks, and be reasonably priced.
Regards,
Steve
Total posts : 45366It’s always nice to hear from the source, and thanks for inviting us to visit your site,
http://www.classeradio.comExperimental broadcasting for a better tomorrow!
Total posts : 45366The reason for the Class E Web Site
Many people think of Amateur radio as collecting QSL cards, contests, crummy sounding single sideband audio – AND expensive, commercial equipment.
However, amateur radio was created as a Technical service (so stated in the FCC rules), and there are many amateurs who build their own equipment.
Many, many amateurs are using AM, and in fact over the past decade the use of AM on the lower amateur bands has increased dramatically. With AM comes high quality audio, relatively easy to build equipment, and a whole group of technically inclined people with whom to talk ! This aspect of the hobby is very engaging, and the conversations with like minded individuals are extremely interesting, as are most of the people themselves.
Many of the AM operators have audio superior to broadcast stations, and almost every broadcast engineer (at least of AM stations) with whom I have spoken got their start in Amateur radio. I know that’s how I got started, and by the time I was 18 years old and in college, I was chief engineer of a radio station. The hands-on education you get from building your own equipment is invaluable, and the personal satisfaction of making your first contact with something YOU built is irreplacable! And a big plus – you are not limited to 100mW of power 🙂
The FCC has recently dropped the Morse code requirement for amateur licensure. This has been a barrier to otherwise interested persons, who want to try hobby radio, but didn’t want to, or couldn’t learn the Morse code.
The written test is SIMPLE, and all of the actual questions that are asked on the real test are available on the Internet and in numerous books on the subject.
Part 15 is certainly fun, but anyone who is interested in delving into something where you can really get your hands dirty with high power, high fidelity transmitters should consider getting an amateur license.
There are MANY MANY people with whom you can talk, ask questions, get help, etc. etc. The AM amateur community is particularly helpful in assisting and mentoring folks who want to get into the hobby.
Something to consider 🙂
Regards,
Steve
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