Hi Everyone
I was wondering if there is a way to match a 3meter antenna to the Ramsey AM25 without
Hi Everyone
I was wondering if there is a way to match a 3meter antenna to the Ramsey AM25 without
using some over sized loading coil. Say like a transformer coupling of some kind. I know loading coils work,
but could we get a higher Q point by using a transformer coupling. Tolroid type transformer,or anything
else that may work. I just wondering if there is a way of tricking the Transmitter into a way that it thinks
it seeing a 50 ohm load from the antenna. Well has anyone tried something different than a loading coil
at the base of the antenna???????
I thought it might be interesting if we could come up with something different from a loading coil at the base of the antenna...These Loading coils get pretty large and have losses of their own in the coil.
Anyways I am open to new ideals that people have tried.
Thanks SKW40
Hi Sean,
I had built an antenna "tuner" for another purpose but found it worked well with the AM-25. As I previously reported here the AM-25 tolerates a rather wide range of resistive load (20 to 100 ohms by my tests) and this is probably why this worked. I make no claims that it is optimized nor claims that it will work with other transmitters. I didn't try to optimize it by changing the turns ratio, etc. since it gave me the range I wanted.
I wound 79 turns of #12 plastic insulated wire on a 1 1/2 inch PVC form. The "cold" end is attached to a copper water pipe in my basement. The hot end goes to a 3 m antenna. Across this coil is installed a 470 mfd variable capacitor. I wound a primary winding of 7 turns over the cold end and this is connected to the transmitter antenna output and ground. I used a scope to tune the cap for maximum field strength and observed a really sharp tuning peak. The reason I used a transformer arrangement was to avoid a ground loop between the antenna system and the audio system and I have no audible hum as a result.
The antenna and "tuner" are mounted horizontally on my basement ceiling inside my stucco house (with metal screening under the stucco). Not the ideal for good radiation but, as I mentioned, it met my needs which were to cover my property.
I had a listenable signal out to about 0.2 miles and could detect my signal out to about 2.0 miles. It was then I discovered that the AM-25 exceeded the 100 mW input power limit by quite a bit, and considering this and the rather poor audio performance on high modulation I decided to retire the AM-25 in favor of the SSTRAN.
I use my SSTRAN with the same antenna but had to leave R18 in the circuit to achieve good audio and clean RF. This is probably due to my "tuner" not presenting an acceptable load to the SSTRAN but since it covers my property well I just left it be as it is. The audio sounds better than the commercial stations here and I use it daily as I wander around here listening to "my" station rather than those of the big boys.
Neil
Hi Neil
You know What I am going to try that...It sounds just like What I need. Thanks Sean