I think the other transmitter you are thinking of Rich, is the Spitfire, which is still available. This is a newer transmitter which has more features than the Spitfire. It has a display that can display the operating frequency or wavelength, as well as the modulation depth - a rather useful feature, I think. Unlike the Spitfire, it also has adjustable gain on the audio input. As you say, it has the options for feeding the audio via bluetooth, and a remote control.

Tony has other AM band transmitters too, but they are higher power and are definitely not Part 15 compliant! Tony's a cool guy. We've been chatting a bit recently via email.

I've been contemplating the purchase of either a Spitfire or a Hurricane, but am leaning towards scratch-building a clone of the SSTRAN AMT-3000. I used to have one, and regret selling it now.

Oh, this is the Spitfire transmitter, by the way - 

https://www.6v6.co.uk/transmitters/spitfire-am-solid-state-transmitter-usa.html

The Spitfire probably is what I was originally thinking. But as for the Hurricane, I'm not to keen on the bluetooth streaming option, but am intrigued by the bluetooth remote control, but it's not clear to me what exactly it does. But it is clear that it gives remote access to the same readings as the led display of the transmitter itself.

The app for your phone or pc seems a streamline to the whole thing of remote control, which is cool, but it's only for the xmtr itself and not for transfer of files or controlling automation. (Just to be clear)

It's a remote status indicator, which is cool as hell. I dont know that I've ever heard of anyone using the Hurricane.

I agree with you about the Bluetooth Rich. It's just another potential point of failure in the transmit chain. I prefer everything to be hardwired. As for the remote control, it strikes me as a convenience, but not essential. If I were purchasing this transmitter, I'd be tempted to get the extras "just in case".

I have come across a few online reviews of the Spitfire. It used to be available as a kit, but is now only available ready-made. I see less online talk about the Hurricane, though I did come across these two reviews - 

https://philcoradio.com/library/index.php/shop-talk/rons-radios/review-6v6-electronics-hurricane-am-transmitter/

and - 

https://swling.com/blog/2023/05/frans-purchases-the-hurricane-am-modulator/

I regret selling my AMT3000. It wasn't the best option for an outdoor transmitter, if you want to maximize your range, but it was great for anyone just wanting to send audio over the AM band to radios around the house. It had the advantage of an onboard audio processor. It wasn't really "proper" audio processing, as it provided compression and limiting in just a single channel. Modern broadcast processors split the audio into 3 channels or more. One of the problems with single channel processing is that heavy bass or percussion can cause the gain to "pump". Electronic Dance Music (EDM), for instance, can suffer with this type of simple processing. In the past, all broadcast processing was of this type. It's the modern bass and percussion heavy music that suffers the most. If you're running more of a legacy format, you'll probably do fine with a simple processor. The built-in processor in the Procaster is this type too (I think it uses the same chip, an SSM2166).

Neither the Spitfire or the Hurricane have onboard processing. However, I think a lot of users aren't too bothered and those who are will want to use their own outboard processing anyway.

I read the review from the Philco Radio site (it kind of surprised me for it to be there). It sounds like maybe the Spitfire and the Hurricane are the same transmitter, with the latter having additional bell and whistles. 

He talks about his SSTran3000 failing which what led him to get the Hurricane...

I had powered up my SStran a few months ago for the for the first time in 4 or 5 years and discovered something not right with it. Last time I put it away it sounded great, but now it sounds fragmented (for lack of a better word), best I can explain is that it sounds like a bad connection not letting the signal out. I haven't mess with it again, I'll be using the Rangemaster when I resume anyway, but it disappoints me, it's not been uncommon for me to grab the SStran and slip it in my coat pocket for use at some impromptu whatever.. on several occasions anyway.

I prefer external processing myself, but don't have the gear anymore so..

I've speculated that the Procaster separated the onboard proccessor from the unit (they did move it right?) because it might have interfered with other components on the circuit board. -:but I dont know, it just seems to explain it.

But back to the Hurricane, what exactly does "Crystal controlled Digital Frequency Synthesizer" mean?

@richardpowers  SSTran experience:

I had powered up my SStran a few months ago for the for the first time in 4 or 5 years and discovered something not right with it. Last time I put it away it sounded great, but now it sounds fragmented (for lack of a better word), best I can explain is that it sounds like a bad connection not letting the signal out.

I had a similar problem with my AMT3000. By removing and re-seating the IC chips every thing worked again and life was fine.

The idea that the Hurricane might be a Spitfire with bells, whistles, and LCD screen controls, is the same thing Ramsey did with their best FM transmitter: the FM35 contained a set of LCD screen control features built on top of the more basic FM-25.

@richpowers Means a digital frequency display as opposed to dip switches but all our transmitters are crystal controlled frequency PLL synthesized. This transmitter actually has the antenna voltage on screen to check the peaking, not a meter.

It's a good idea if storing electronics like transmitters or hi fi as Rich did for 5 years and now didn't sound good, a good idea to once every few months to power up and let run for a bit to preserve the electrolytic capacitors as they degrade more over time if sitting unused. Those are the weak link in all old electronics especially if store and never used.

@rugster The only way to stop the "pumping" is to have multiband compressors like the Schlockwood or Sean cuthbert. A demo of this...

@richpowers  - if you ever want to sell your SSTRAN, let me know. I decided a while back that I'd buy an AMT3000 (or 5000) in almost any state, working or non-working because, in the worst case scenario, I could completely disassemble the board, clean it up, and rebuild it. When I read on the Philco site that the author's AMT3000 had failed, I was going to offer to purchase it from him, but then found that he had passed away. Anyone else reading this - if you have an AMT3000 or AMT5000, I'm interested.

I was also wondering if the main guts of the Spitfire and the Hurricane are similar. There's quite a lot of extra circuitry in the Hurricane though. There's that microprocessor board that controls the extra functions (Arduino compatible, perhaps?) and the little OLED display. Plus, there are the header strips, which I presume are for plugging the optional Bluetooth board in. If my recently reawakened interest in Part 15 continues, I may end up with either a Spitfire or a Hurricane - or both.

I also prefer external processing. A lot of Part 15'ers seem to like using a computer to do their processing, presumably because it's often a cheaper option. I don't like it though, because it introduces one extra point of failure. Computers can go wrong, need restarting, updating, etc etc. Processing done in hardware and/or firmware just keeps on running. If there's a power outage, it starts right up again when the power comes back on. It's more reliable.

Oh yeah, about the phrase "crystal controlled digital frequency synthesizer". It could mean a number of things. I've tried to find a clear picture of the insides of the Hurricane, to see what devices it uses, but the only one I can find is from that review on the Philco site, with the interior photographed from an angle. I was hoping to find a nice, clear picture shot from directly overhead. Firstly, virtually all of the Part 15 transmitters we discuss derive their frequency control from a crystal in some way. The only ones that don't are the cheaper ones from eBay, that use a coil and variable capacitor for tuning, and cost $50 or less. They tend to drift in frequency, and setting the frequency accurately isn't as straightforward. The older tube transmitters, such as the Knight Kit and the so-called phono oscillators, also often used a coil and variable capacitor for tuning. The Spitfire, Hurricane, SSTRAN AMT3000 and AMT5000, Procaster, and Rangemaster all derive their frequency from a crystal. This is where my understanding of the methods used begins to fail me. I know that the SSTRAN transmitters, and probably also the Spitfire, use digital dividers to divide the frequency of a crystal down to either 9KHz (for Europe) or 10KHz (for the USA versions) for the steps between channels. That same reference frequency is also multiplied up to create the specific frequency selected, which is compared against the frequency generated by a VCO (voltage controlled oscillator). A PLL (phase locked loop) compares the two and generates small control voltages for the VCO, to keep the VCO on frequency when it drifts away. It is the signal from the VCO that is amplified and modulated, to provide the final output to the antenna.

Sorry - that was an overly-wordy and probably confusing explanation. These PLL-based transmitters work well, but are not quite as frequency stable as other methods. It only matters if there is a very weak station on the same channel, when you want the best stability possible, so that the fluttering sound that is generated between by a beat between your station and a competing station on the same channel doesn't vary too much and become annoying. PLL's do tend to "hunt around" slightly as they are correcting the frequency - it's how they work. Keith Hamilton says that his fixed frequency modules are more stable than his frequency agile module, which uses a clock generator chip that also derives it's reference frequency from a crystal. I don't know how his fixed frequency modules work. I have a number of his fixed frequency modules, for all the channels from 1590-1700KHz, as well as his frequency agile module.

As for the Hurricane, it might use a clock generator chip. They use an internal PLL circuit, so I don't know whether they are more stable. Then there is a method of frequency generation called Direct Digital Synthesis (DDS). I *think* those chips work by using a complex scheme of frequency multiplication and division to generate the precise frequency directly from (once again) a crystal, without the use of a VCO and PLL, but I don't know. At this point, I'm just blowing hot air and guessing!

Sorry for all the words. I just can't help myself sometimes 🤣 

I think there have been other replies while I was typing all this word soup, so hopefully these comments haven't been rendered irrelevant.

Posted by: @mark

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@richpowers .. but all our transmitters are crystal controlled frequency PLL synthesized...

Both my Rangemasters are crystal controlled - unfortunately I only have only one crystal, 1700. I used to have a 1630 crystal too, but don't know where that dissapeared off to. Keep hoping it will turn back up but not holding my breath.

(That reminds me, I never got a reply from Kieth when I emailed him about his site a week or two ago.. He's always been one who promptly replies to everything.)

@rugster I'll have to give your post a re-read later (I get carried away sometime too) when I can better absorb it.

As for my SStran3000.. I'm going to try "re-seating" as Carl suggested... If that doesn't remedy it.. I don't know. I really liked this little thing though my use of it has always been sporadic. However, if it not working right I seriously doubt I will ever make an attempt to fix it - I would have no idea what to do!

If worse comes to worse, and I cant do anything with it, I'll probably give it to you because I know you could remedy its ills and make more use of it than I ever hsve..

But I just dont know what I might do with it at this point. I dont really need it, Ive got two Rangemastets, but it's just that, once it's gone, its gone.. and I dont want to regret letting go later.

Maybe is an aggravating word. But at the moment that's all I got.

@richpowers I completely understand. Once it's gone, it's gone. If I were in your position, I'd take plenty of time before making a decision. In the meantime, who knows - re-seating the chips may have it back to working order in no time, and you'll have it for a few more decades!

I think I'd rather buy one from someone who is unlikely to regret it later, or who I don't know, so that I'll never know if they later regret it 🤣 I wouldn't want to feel bad over the acquisition of a hobby transmitter.

Oh, and @mark - I started watching the video you posted it. Very interesting, but now I have chores to take care of and may not be back until much later. Will respond in the next day or so.

@mark Concerning the Sean cuthbert proccessor, I happened to have one in my ebay watch list- not that I was planning on buying one anytime soon (if ever), but so happens yesterday I got an offer to buy it now for $30 off .. 

Even if I had $169 laying around to spend I'd proubly pass and save up for a Schlockwood.. bit damn, is the expense really worth it?

Vv