SpitFire AM Transmitter

Sounds like it doing good with no ground.

Mark

Great to hear it's going, I thought it was probably a decent transmitter, being that the Spitfire has been on the market for some years now.

What did you do to get it going? It might help other Spitfire users. I saw that you changed the frequency to 1500 and bypassed the internal matching circuit, and now it's working and reaching 4 buildings from indoors.

Depending if the Spitfire has a audio level control on the input, you might need a resistive pad to drop the Orban's output level from pro to consumer. I don't know what the Spitfire can take, but it's something to watch out for until you know.

Yeah, The SpitFire has NO input level. The Orban has no working output level. So I drive a cassette deck and use the headphone out to pad down the level. It works good! Loud, clean signal! I'm impressed. 

What I did was, changed the frequency to 1500 and switched OFF the internal ATU. I have an old coax in the wall. I wonder if the shield is grounded...

Doug

I wonder if the Spitfire grounds through the power supply, does the manual say anything about that? Glad to hear you are having fun with AM. Same here, SStran AMT3000 running 24/7 on 1620 AM with talk and Heavy Metal Whether the neigh bores like it or not.

Barry at BBR 1620 AM

Nope, Barry. The power supply is a two prong. I have NO idea how this thing plays with NO hum! My TH 5.0 was a hum box! My SSTRAN had a slight hum as well. This thing...dead air is a slight hiss. Amazing...

Doug

It's easy to drive this thing to distortion. I have no way to measure modulation, since my tuner was removed temporarily. The Spitfire has no GAIN or MODULATION contols. It's pretty much straight in, and drive it till it distorts and then back it off. The Big Boys don't do it that way...

I need to find a decent AM Mod Monitor, cheap. A Belar would be epic! Right now, I have a Denon tuner driving a Sanyo Cassette deck that's locked into Record mode. I find a local AM station and set levels to 100%. I then match mine to that. It works. 

But this, I have to set by ear. I got lucky, I guess...

Doug

You know if there was a way to get some actual range with that Spitfire I’d switch to that for my AM Transmitter. I have a TH5 and its a piece of pure T junk as far as I’m concerned. The audio sounds like a Fisher price toy transmitter. I’ve even heard a Plannet DJ from the Sears catalog back in the 70’s sound better than that horrible thing.

The fact that the spitfire doesn’t hum is a major plus for it. I wonder how much one costs? Maybe I should try that one out with a wire connected to a 6 Ft piece of copper pipe. If it has a built in ATU I could tune up to it just fine. All i’d need is a few inches of wire to connect to the pipe. Maybe simply a roach clip or just have a screw on the bottom of the pipe and screw the bare wire into the copper pipe.

With no hum and good audio at least I’d have HQ audio. Worst comes to worst I’d do the same and have a old cassette deck with the VU meters on it and match the meters so that my station is close to the volume of the bigger stations. Even the old turn till it distorts and back off ¼ turn does work in a pinch. Its what many low power stations did in the day when people actually could hear and appreciated good audio but didn’t have the mega bucks.

I suppose Auydacity and its meters too could work for setting modulation and comparing it to the bigger stations. Get a close match and your all set.

You can deduce your modulation level by listening several channels away for clipping of the carrier, with your signal at a loud, but not overpowering level on a radio.

If you're on 1500, then listen on 1530 and higher, or 1470 for splatter, it varies with how much overmod you are.

Wow, thanks guys! I do need pro equipment to do it right. I ain't paying a thousand dollars, though...

Hey, this blows away the TH, sound-wise. Now, If I made a serious loaded coil whip, and used the internal ATU, I bet this thing would make it downtown! The TH did that no problem, but sounded like a telephone.

But I ain't done with the SSTRAN. I gotta fix my problem first. But I have enthusiastic neighbors. So I run the Spitfire. And I like that it's made in the UK. They are known for excellence in broadcast equipment. My Veronica 30-Watt FM Stereo transmitter is a fine example. Although not on the air, it sets the bar. Rock solid and clean!

This Spitfire is in that league. Although bare minimum, it holds its own! Literally plug & play, assuming you don't change the 1440 kHz frequency. Up here, 1500 is clear. And I am amazed at no hum! There is no Earth ground up here. I got a two-way plug on the power supply! Baffling.

Doug

"It's pretty much straight in, and drive it till it distorts and then back it off. The Big Boys don't do it that way..."

You would be very, very surprised. LOL!

Radio transmissions do odd and funny things when over-modulation occurs. Imagine a 50,000 watt blowtorch like WRKO winging it! Ha!

I see the AMM3 Belar just went for $775 on the auction site. Too much. My retirement pension can't cover anything like that. Oh well. That's why we wing it! Ha!

Doug

The full power I'm at doesn't have a mod monitor either, modulation levels are set by cranking up the audio till the transmitter shuts off, then back it down from there till it stays on. There are a few stations here that have either no mod monitor or a broken one. The biggest stations definately have the correct gear however but don't be surprised if your local mom and pop just "wings" it lol!

",,,modulation levels are set by cranking up the audio till the transmitter shuts off, then back it down from there till it stays on."

Awww MAN! Mark Osbourne would go balllistic! He is a station owner who has always done it right. By the book. I learned a lot when he built KISS 94. Imagine setting modulation levels by cranking up the audio till the transmitter shuts off, then back it down from there till it stays on! Haa haha! That would only happen ONCE! LOL!

Doug

The reason I asked about the Spitfire grounding through the power supply, was that the SStran offers the option to ground through the walwart power supply using a jumper.

If the jumper is not used, the sstran will ground through the antenna ground connection.

EDITED TO INCLUDE SCREENSHOT:

Barry