I haven't had an AM transmitter since I was a kid and it was a one tube type. I don't remember the brand or anything. I thought about using an FM transmitter. but noticed the FCC is more likely to fine one for using even a low powered FM transmitter, so I decided to see what is new with AM. After much research and reading many reviews, I decided to purchase a SSTran AMT3000 AM Transmitter.
As has been stated by many others, the kit arrived nicely packaged with all of the components separated. I would rate packaging at 100%. Shipping was very fast and I would also rate shipping and ordering, as well as customer service 100%.
I managed to assemble the transmitter after being up all night the night before. Couldn't sleep well:) It took me about 8 hours, but I was careful and took my time. It has been many years since I assembled a kit, so I was being a bit overly cautious.. I am 52 so I needed to use some assembly aids...LOL With adequate sleep, after having assembled this transmitter I am sure I could assemble another one in under 3 hours. Unless you are good with SMT's I would recommend having the SMT IC soldered on for you when you order the transmitter. I did, and it only costs an additional $3.00.
The manual is straight forward and very clear. It is full of information explaining what the various circuits do as well as other valuable information. I believe anyone assembling the kit, and reading the manual, will learn something new. The assembly instructions are very clear and straight forward. The only place I needed to use a meter during assemble was on the resistor network. I wasn't sure if it was marked properly as the markings and part number were barely visible, even using a magnifying lens. I confirmed with the meter it was marked properly. This was the only problem I had during assembly. I did mount all the resistors and ceramic caps first. This makes it easier when turning the printed circuit board over to solder, as the board will remain level enough.
After assembling and testing, the unit did work perfectly. It is easy to mount to the case. Everything fits perfectly. This has restored my confidence in kit building and I am very happy with the SSTran. The unit is very easy to tune. I tested the range and achieved around 300' of "usable range" in my car. This was done using only the ground wire supplied and not attached to anything, and the supplied antenna looped around the window on the inside. So while not totally surprised, as I have read many reviews, I am impressed.....especially with the sound. It's awesome for an AM transmitter at this price range.
My studio is computerized. I use OTS DJ software and it works really well with the SSTran. I have tried the transmitter with the built in compressor/limiter and it works very well too. So you don't need any expensive equipment to set up a studio and it will sound as good, if not better than some of the commercial AM stations.
I tried doubling the length of the included antenna, and grounded to the same ground my satellite dish uses. I live in a mobile home and the dish is grounded to the frame. I know the limitations of part 15, but I live in a rural area so I am not too concerned. I did notice the test voltage go down after doing this. I found the grounding was improving the range, adding more wire really didn't help. I am running mine on 1620khz.
There isn't really much I can think of to improve the transmitter, although it would be nice if it could modulate up to 125%. An on/off switch and tuning indicator might be nice bit are not really necessary. This transmitter can be tuned with a cheap DVM.
I have researched antennas including the one on the SSTran website and the antenna guy. I did look at the Isotron, but I am not sure how well it would work for part 15 AM, and it costs $248.00. I have not found anyone yet that has used one with a Part 15 transmitter.
www.isotronantennas.com/ambroad1.htm
I ended up purchasing a Valor PHF160B 160m MOBILE ANTENNA from R&L Electronics. I know it is a 160 meter antenna and designed for 1.8 to 2.0 mhz. My range has doubled using this antenna, and I don't even have it outside. I have it mounted on a camera tripod in my home. To repeat, I have Dish Network, and it is grounded to the frame of my mobile home. So I am using the coax from that to ground the SSTran to. I tried my cable ground and electrical ground, and found the frame of my mobile home works much better than anything.
I did modify the SSTran to work with a coil loaded antenna as instructed in the manual. The only difference is with the S5 switch, I need to leave 1 in the off position so the 56uH inductor is activated. This is the only way I can get the voltage high enough to work with the Valor antenna. I am thinking a more efficient inductor would help the range and I still need to try it.
Currently, the usable range in one direction is around 2000', where as in the opposite direction it is around 500'. I am certain this is because of trees. One thing I did notice is it seems the higher the Valor is, the higher the voltage. So perhaps it would resonate perfectly if it was 20' or so high using its own coil, and would not need the SSTran inductor activated, or another coil, for it to resonate. I am sure if I ever get it outside the increase in range should be dramatic.
I have some ideas for mounting outside. My biggest concern is lightning. Fortunately I have a shed that is wired for electricity and I could find something cheap to use for a wireless link. Therefore, I could have everything out by the shed except for the studio, and possibly mount the antenna on top or along side the shed. I only need a half mile of good range to cover my community. I am not sure what I would do as far as grounding, perhaps a ground rod would suffice. I have noticed some people have had good results with chicken wire.
I found a good case to mount the unit inside of. I haven't ordered it yet but the specs are good and the price of the case is reasonable. The link for the case follows:
www.hyperlinktech.com/web/weatherproof_wireless_enclosure.php
I think the only question I have for now is would mounting the Valor antenna higher help it to increase the tuning voltage? Would using an efficient inductor help? Perhaps someone can help me with this, and maybe Rich would be kind enough to use his expertise to help 🙂
I'll be stealing a copy of that for our trasmitter review section, too 🙂
Experimental broadcasting for a better tomorrow!
Thank you. I am experimenting with a cheap wireless link. Actually it is one of those wireless 1.2ghz video transmitter/receiver combos. But it works well just using the audio part of it. The transmitter is 50mw 🙂
Before, I had been using a long audio cable from the transmitter to my computer. With this setup, I was not using the audio and power RFI suppression coils and had zero hum.
Using the wireless link, there is little difference whether or not I use the suppressors. There is however a bit of hum. I am using a 12 volt switching power supply on the links transmitter and receiver, so I know it's not coming from there. I still need to try a few more things as this is kind of an experiment.
I really enjoyed re-reading the beautiful review from Michael for the AMT3000, and my post now ties right into his experience, because I also have been running two AMT3000s since back in 2007, and I still love them so much I actually sleep next to one of them because I have better dreams.
Anyway, I recently designed a triangular loading coil and got the antenna to full resonance according to the book, and that part of it was perfect because it gives a solid signal everywhere in the house and out in the yard, but the signal falls off in the public, where I am not trying to bring radio to strangers.
But I recently noticed an industrial hum below the audio, and began tracing the audio line, which is a 25-foot unbalanced string of 7 different types of connectors.
To really get me concerned, I this morning noticed that the buzz on either side of my carrier out to 30kHz on either side made me sound like an HD iBah station, and it was a by-product of the hum, which therefore made me think RF from the loading coil was inducing its way into the audio.
A toroid on the audio line did nothing.
Finally, I went down the line and re-seated all the connectors and "zing" the hum and the buzzing went away!
Lesson learned: typical consumer audio connectors are bad news and bring trouble.
What I plan to do is go to a balanced audio line with screw-down terminals, no consumer connectors.
Congrats, Carl, on utilizing your troubleshooting skills. Often we tend to attribute technical troubles to obscure, though plausible, causes and overlook the most common causes.
Over the years, the biggest problems I have had with audio equipment is noise and distortion caused by connectors. The "RCA phono pin" connectors are the absolute worst in my experience to the point that I avoid using them when possible.
Perhaps the most reliable audio connection system was developed well over 100 years ago and is called the "1/4 inch phone" plug and jack. I have used these for over fifty years in systems handling signals from microvolts to hundreds of volts and nano amps to a hundred milliamps without a single problem caused by these connectors.
There are many other fine connectors suitable for audio but the RCA phono pin is the worst I have encountered.
Neil
The buzzy side-carrier problem returned and this time I can't get it to shut up.
Looking at the spectrum analyzer we see that the buzzy side-carriers are NOT appearing with visible peaks of their own, so I think I'm within legal bounds, but still intend to re-design the audio line without the RCAs.