50watt TX Pics

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piratefm
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50watt TX Pics

Post by piratefm » Wed Jul 13, 2022 11:00 pm

Hello!

Just thought I’d show you guys the “guts” of a transmitter I recently got. Made by E.T Broadcast. 50watts & RTTE/CE compliant. Was recently removed from a station here in the UK.

https://ibb.co/album/Pz7g4X

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Re: 50watt TX Pics

Post by XXL » Thu Jul 14, 2022 9:28 pm

It’s what compliant ? That looks exactly like a pirate transmitter.

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Re: 50watt TX Pics

Post by piratefm » Thu Jul 14, 2022 10:19 pm

XXL wrote: Thu Jul 14, 2022 9:28 pm It’s what compliant ? That looks exactly like a pirate transmitter.
If a transmitter is R&TTE Directive & CE compliant it means that it can be put into service at an Ofcom licensed station.
It may well look like a pirate rig but it's not, it's been in service at a community radio station and passed the tests that Ofcom set before it can go on-air. The only reason for removal was further power was required due to them being granted a Power Increase.

It also requires that the transmitter's settings can not easily be tampered with. So to change any settings on this you need a small screwdriver to change the trim pots etc.

More can be found here on the Engineering code:
https://www.ofcom.org.uk/__data/assets/ ... de2013.pdf

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Re: 50watt TX Pics

Post by teckniqs » Sat Jul 16, 2022 5:59 pm

No it doesn't look exactly like a pirate transmitter it looks exactly like a lower-budget legal spec transmitter.
The seperate PLL is very common in commercial FM transmitters, the SBS LP2 is very similar inside.

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Re: 50watt TX Pics

Post by Albert H » Sun Jul 17, 2022 1:32 am

My legal 25 Watt transmitter design was built in a 2U 19" rack case, and had everything inside on several boards. There was an exciter board that would give 200mW anywhere on the band, a PA board with a BGY133 module amplifier, a lowpass filter board mounted on to the back side of the N-Type RF output socket, an audio processor board with 15kHz lowpass filters and a three-band limiter, a stereo coder board, an RDS board, and a monitoring board that gave temperature, SWR, over-modulation and other alarms. There was a linear PSU in the case too - the whole thing was pretty crammed, but it provided balanced stereo line-level audio input and RF output through back panel-mounted sockets. The mains supply came in up an IEC ("kettle") lead....

Frequency setting and limiter adjustments could be carried out by opening a front-panel flap. It had facility for several ways of setting up the limiters according to the type of station it was to convey. It could be set up for "loud and punchy" for pop and rock stations, really fast acting for talk shows, and a slower, less obviously processed sound for jazz and classical music.

If I can find one of the old brochures, I'll scan it and put it up here!
"Why is my rig humming?"
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Re: 50watt TX Pics

Post by piratefm » Sun Jul 17, 2022 11:54 am

teckniqs wrote: Sat Jul 16, 2022 5:59 pm No it doesn't look exactly like a pirate transmitter it looks exactly like a lower-budget legal spec transmitter.
The seperate PLL is very common in commercial FM transmitters, the SBS LP2 is very similar inside.
I’d like to see the insides of a SBS LP2, from a geek perspective!

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Re: 50watt TX Pics

Post by teckniqs » Sun Jul 17, 2022 3:14 pm

piratefm wrote: Sun Jul 17, 2022 11:54 am
I’d like to see the insides of a SBS LP2, from a geek perspective!
SbS Driver.jpg
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Re: 50watt TX Pics

Post by Albert H » Sun Jul 17, 2022 11:33 pm

That SBS box used to have all sorts of spurious nasties! The output spectrum was rather poor, and the baseband content left a lot to be desired. It suffered a lot from trying to cram everything into the one box (something I used to be guilty of too, but I was more careful with the layout and avoided the pitfalls Py*** fell into!
"Why is my rig humming?"
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Re: 50watt TX Pics

Post by piratefm » Mon Jul 18, 2022 6:54 pm

Albert H wrote: Sun Jul 17, 2022 11:33 pm That SBS box used to have all sorts of spurious nasties! The output spectrum was rather poor, and the baseband content left a lot to be desired. It suffered a lot from trying to cram everything into the one box (something I used to be guilty of too, but I was more careful with the layout and avoided the pitfalls Py*** fell into!
I find that interesting considering there are still SBS boxes in use across stations.

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Re: 50watt TX Pics

Post by Ignite » Mon Jul 18, 2022 9:45 pm

I've just been taking a look in my archives, and I've got the full manuals for a number of the SBS FM transmitters and exciters (FM10, FM25, FM30 Mk1 and Mk2, and PA250). These all include the schematics so if anyone is interested, send me a PM.

I always found their naming of the FM25 a little strange as it only gave 17W max where as the FM10 gave 10W and the FM30, 30W. I've used both the FM25 and FM30 in the past for RSL broadcasts, and both were reliable transmitters.

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Re: 50watt TX Pics

Post by teckniqs » Mon Jul 18, 2022 10:42 pm

piratefm wrote: Mon Jul 18, 2022 6:54 pm I find that interesting considering there are still SBS boxes in use across stations.
I get the strong impression it's much more of a personal issue with the owner of the company and not with the true spectral output of their equipment. :whistle

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Re: 50watt TX Pics

Post by Ignite » Mon Jul 18, 2022 10:58 pm

teckniqs wrote: Mon Jul 18, 2022 10:42 pm
piratefm wrote: Mon Jul 18, 2022 6:54 pm I find that interesting considering there are still SBS boxes in use across stations.
I get the strong impression it's much more of a personal issue with the owner of the company and not with the true spectral output of their equipment. :whistle
What was the spectral output of their later models like? I've seen them in use in some commercial radio stations that I've worked at, and they seemed to be OK. No noticeable harmonics even when standing next to the tower. This was for example a TX25 feeding a PA250 and then going into a circular polarised antenna.

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Re: 50watt TX Pics

Post by Albert H » Mon Jul 18, 2022 11:37 pm

The original SBS rig was used for LGR at Alexandra Palace. Its spectrum would NEVER pass muster - there were scurrilous rumours of dodgy dealings at the time. I had a house less than a kilometer from their site, and it was all over the band and up into Band III as well.

Later versions were very much better, and had (in some cases) some fairly innovative circuitry. SBS learned from their early mistakes, and some of their gear has proved to be very reliable over the years.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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