"Our station is a staion with no format. We don't fit the commercial boys idea of a pigeon-holed top 40, classical or hip-hop station."
Mram,
Come to think of it, many of the high schools stations in Southern Ohio were open format and did have listeners. Some of those listeners were pround parents, others were die hard Alumni who love their school station.
Scarlet Oaks Voc. School WJVS-FM (D) was more of a top 40 station spinning 45's, not sure we had many listeners besides the ladies in the office upstairs, i played classic rock after school for an hour and half before we signed off the station and turned the frequency over to WAIF-FM.
My high school, Clermont Northestern had a station for several years that shared a frequency with WOBO-FM Batavia Ohio. That format was all over the place, i didn't get involved with WCNE-FM but was later on WOBO-FM as a volunteer DJ.
As i said, not many high school stations left in the Greater Cincinnati Area which is a shame.
Down here there are few student run stations, even one on AM with a few thousand watts.
Barry of BBR 1620
WOES was a High school station running 100 Watts I think it was 91.5 Mhz. It broadcasted around 1979-1985 or so and my friend Dean played some great Album Rock. The format was Adult contemporary during school hours till 3pM and Rock till 5 PM Mon-Thurs and Friday Rock after 3pM-9pM. They too had listeners.
Anyone wish to comment on the SpitFire AM Transmitter?
🙂
Doug
Dugger,
I am curious about the ATU section of the Spitfire.
What do the instructions say about it's operation?
How does it work? Is it hand tune from a pot in the transmitter or automatic?
Barry
There is a 4-DIP Switch ATU and a trimmer cap, Barry. I had no luck with it at 1530. I switched the ATU to the OFF position and changed to 1500 and BOOM! A 10 foot wire! All over the place! Two houses on either side of me, one in the back and several across the street and in the cul-de-sac.
I have the antenna taped to a six foot piece of wooden trim, and that is mounted on my camera tripod. I'm on the 2nd floor corner, so I put the antenna in the corner. Pre and post sunrise, it's terrible, but once the sun comes up, she beams!
There is mention of using loaded coils with the wire antenna. 300-400 uH is recommended. Never done that. Wound a coil, that is. My neighbors seem happy with it. Just can't do a damn thing at night, That's why I bought a Part 15 FM Transmitter. Not sure how that's gonna work out. It was a very good deal.
But the SpitFire has potential to be a little blowtorch! Very much like the SSTRAN AMT-3000. I need to play with the ATU some more. I'm just afraid to wreck the coverage I have now, if I change something.
Doug
"Pre and post sunrise, it's terrible, but once the sun comes up, she beams!"
Night time is a good time to tinker with the tuning when your coverage is limited to a smaller area. I do my best work at night despite getting older and my body craving sleep.
I am curious now, if it's doing that well now on just the wire antenna what would it do on a coil loaded vertical with ground elements.
Barry
Do you have a Smartphone? If so I suggest taking pictures of how it is set now. Then you can always go back to where it was. I know a hair turn of a variable cap can make a huge difference.
I've seen a picture of the Spitfire's board on an auction, and it looks like the tuning is similar to the older AMT unitswith molded inductors selected to be in or out of the circuit by 4 dip switches.
That means you can set the switches to use combinations of inductors in series that get the system close to being resonant with the antenna connected, and then using the tuning capacitor for final tweaking for a maximum power output peak.
The capacitor should be across the junction of the last output inductor and the antenna, and ground, and should be a low loss dialectric cap.
I've noticed that most of the Part 15 transmitters on the market have similar output circuits. The components may be different, but the circuit is similar, probably because it's a tuner that really works, and it's simple enough.
It's pretty much a straight 'L' network, transforming low into high impedance for the short antenna.
The older AMT 3K uses the set of moulded inductors, the newer 5K replaces the inductors with what looks to be a powdered iron toroid, something like a T-200-2, that would have better efficiency on the broadcast band than than the small inductor set.
Instead of switches, it uses jumpers, but really, it's doing the same thing, selecting sections of the coil in and out of the circuit, and again, the output variable capacitor peaks up the circuit for highest output.
The Rangemaster looks like it's based on the same idea, while the Chez Procaster is the only common commercial transmitter I know of using an air core inductor, no core. That could help by being lower loss, no ferrite or iron magnetics to cause losses, but the Chez's coil also isn't adjustable, meaning you're likely going to end up using more capacitance than if you could select coil taps.
You want the most inductance, least capacitance for the highest efficiency, and the more inductance you can use, the less capacitance you'd need to get to the peak output.
A little capacitance across the output at the antenna is good so the tuning is more broadband, but too much will kill the efficiency of the circuit.
I don't know who first pioneered that style of tuner for P15, the large inductor, small cap L network, but everyone seems to use it now, and it was probably one of the larger breakthroughs that made the commercial part-15 transmitter possible.
Older circuits always seemed to use a parallel resonant circuit, a coil and capacitor output tank, with the antenna wire attached to the top of the coil, the high impedance end, especially with tubes. Transistor circuits carried that on for a while.
This is valuable info. Coils, capacitance and inductance...OH MY! Outside my expertise. I am just amazed at the sound of this little box! Cyndi Lauper is singing "All Through The Night" right now. Yeah, it's the Orban, I know. That DOES make a difference. Incredible. And the neighbors love it! Wait'll they hear the FM! LOL!
Doug
I'm always reading and learning plus experimenting and trying to think up something new, all this RF has fried my brain maybe!
I'm glad you like the Spitfire, it has to be one of the best deals in a transmitter out there, built or not, it seems like a good basic circuit that's engineered well, since you report good sound.
I don't think that some other transmitters are that well engineered, like the Talking House and the Ramsey PLL, AM-25 I think. Those have good points, but shortcomings where it hurts, the sound quality.
i'm thinking of getting one after i seen what you said about it cool thanks
i was wondering if this transmitter was good i mite try to get one
You mean, "Might"? Yeah. Good little unit. On on eBay right now...$90+
Doug
This Spitfire transmitter you speak of. From the UK. Non FCC certified. It's illegal for them to sell them here without certification. Of course it's legal to operate one as long as you are meeting the Part 15 AM rules. But it is not legal for them to sell one here without certification.
Which also means that should the FCC visit you you will need to be prepared to show that you're meeting the rules and you have no certification to back you up.
Just pointing out a technicality. Not necessarily one that would get anyone in trouble here, as long as you're operating legal.
TIB
From Reply 74, above: ... Just pointing out a technicality. Not necessarily one that would get anyone in trouble here, as long as you're operating legal.
__________
Just wondering ...
How could anyone reasonably expect to prove that the radiation from their unlicensed AM/FM broadcast band transmit system is legal under Part 15, if/when an FCC field inspection shows otherwise?
Even transmitters with traceable FCC certification as being compliant with Part 15 rules when measured in a test lab environment can be installed and adjusted by the final buyer/operator of same so as NOT to be compliant with Part 15.
And likely moreso for such hardware never having been officially certified as compliant with FCC Part 15 -- as shown by the measurements of same reported here by TIB.