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 🙂
Outside mounting
I found a nice weatherproof box at the local Lowe’s for about $24. The lid isn’t hinged, but it held on with screws. The box has no holes. You will have to drill your own. I sealed the holes with RTV. My SSTRAN has been on the roof in this box for about three months now, with no trouble.
I don’t remember if I posted a picture of the SSTRAN mounted in the box before. If not, let me know and I’ll post one.
I built the SSTRAN antenna (modded) and it tuned up just fine. I get out about 1 mile to the truck radio. Weaker reception can be had out to 2 miles.
I would recommend using a scope to adjust the modulation and gain levels on the SSTRAN. Doing it by ear is ok, but for maximum modulation w/o distortion, use a scope. It is much easier to see what you are adjusting if you feed the audio and RF to the scope in X/Y mode. This way you get a trapezoidal pattern (more or less). Of course, if you have a real modulation monitor, that is even easier 🙂
Trapezoidal patterns and other monitoring techniques
Mojoe,
Trapezoidal patterns are a great way to monitor AM and SSB transmissions and it is good that you raise the topic. I have done it here with both my Ramsey and SSTRAN transmitters (as well as for HF on the ham bands). There is a slight problem, which is solvable with some filtering, in that the RF leaks into the audio channel on my scope and fuzzes the pattern. It is still useful though. For those with an AM system and a scope, I highly recommend you learn about trapeziodal. patterns. Easy to do and it will show you a lot about transmitter linearity and it is a lot easier to read than a time based display.
Now, for those who don’t have a scope, there is another way to check your modulation on AM. This will not tell you if you are undermodulating, but can indicate overmodulation (= trouble). When your transmitter is operating with audio, take a portable receiver and move away from your station. You should be far enough away that your signal is “average” and not strong. Tune up or down a bit from your frequency and listen for a “scratchy” sound that corresponds to your audio. If you hear this, you are probably running the audio too high. This is not exact science and if you don’t hear the scratching it doesn’t mean you are OK, but it can usually catch a problem. It is also possible you will hear the scratching even though things are OK. Experiment a bit by varying the audio levels and you will learn by experience what to listen for.
This doesn’t work if you are near your station and it is important to be far enough away that your signal is not too strong.
Here, I use a scope to verify my settings on the SSTRAN and have found that it is pretty much set and forget although I do keep an eye on the output level of my PC sound card which is my “audio chain”.
Neil
Thank you both
Thank you both for your comments. I didn’t even think about checking the hardware store for a box. Next time I go I will look around.
No doubt I need to get a scope. I did use them years ago when I was in the computer field. So I think I could figure it out, but I am glad you mentioned about filtering.
Anyway, I will try to get some funds together to get a scope, probably off ebay.