Unusual FM IF of 6.75MHz alignment with plots. SABA Meersburg 100 restoration part 6

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In this video, I dive deep into the intricacies of the Saba Meersburg 100's IF alignment process, which boasts an uncommon IF frequency of 6.75MHz for FM. Join me as I embark on this journey, combining the prescribed method outlined in the service manual with my own visual alignment technique using a signal generator sweep function.
To provide a comprehensive understanding of the results, I decided to manually plot the IF response curve before and after each tuning method. The findings are nothing short of fascinating!
Let's dive in and explore together!
Info on 6.75MHz IF:
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[@SereghiAlexandru]

Incredible way to explain and show us how to align a Saba FM. Congratulations!!!

[@electronicsoldandnew]

Thanks 😊

[@johnkris753]

As always 1. Informative 2. Concise 3. EXTRA Meticulous 4. Entertaining That is why I subscribed to your channel. Thank You, and keep this videos coming. Cheers my friend you restored this to perfection again 👍

[@electronicsoldandnew]

Thank you 👍

[@radio-ged4626]

Interesting to see that a manually plotted response curve is so near to a real-time plot. Good to know if you don't have a sweep generator. Although you thought you rushed through your explanation of i.f. alignment, for me it was the clearest one and made sense when corelated with the schematic. Great job.

[@electronicsoldandnew]

Thank you. I like doing some plots on occasion to test the results. Not needed, but fun.

[@DavidTipton101]

Great info Manuel 👍

[@electronicsoldandnew]

Thanks Dave 👍

[@dl7majstefan753]

Very informative dear mauel and congrats to your "new" Simpson.

[@electronicsoldandnew]

Thanks Stefan. The “new” Simpson was a gift from a viewer who visited Madeira from the US. We met for lunch and he surprised me with this beauty 😊

[@dl7majstefan753]

@@electronicsoldandnew Very nice guy ...

[@electronicsoldandnew]

👍

[@richardbrobeck2384]

Nice job on the alighment ! I love using my old Simpson 260 and my VTVM meter for doing alighment .

[@electronicsoldandnew]

👍

[@Joligo60]

Sensacional. Como sempre, uma verdadeira aula. Vários ensinamentos podemos tirar deste vídeo. Parabéns pelo belo trabalho

[@electronicsoldandnew]

Obrigado João 😊

[@gm837228]

Fantastic, high quality teaching video! I ALWAYS learn something from your channel. That's so much for sharing your knowledge. DC4DC

[@electronicsoldandnew]

My pleasure 😊

[@cbiz8]

Manuel: Excelente (Brilliant!) y didáctico como todos tus videos! Saludos.

[@electronicsoldandnew]

👍

[@maartenschapendonk6345]

nice to see the cat's contribution to the antenna input ;-)

[@electronicsoldandnew]

He’s always got to have a say in the project 😊

[@retro_tech]

Great video once again. Thanks for you very elaborate explanation! On the FAQ section of the Dutch forum for old radios, it is mentioned multiple times that it is not advised to simply align the IF for a maximum output reading as this would make the curve too narrow, especially on high end receivers. It seems that this is also what you experienced here. Unfortunately they don't give a good alternative approach except mentioning that "a good technician can correct this by ear". I would like to have a bit more of a scientific approach and your video comes really close to that. Maybe we should look a bit more into this...

[@electronicsoldandnew]

I agree that the instructions here are too simplified, and a full visual alignment is the best option. However, we mustn’t forget that this is a mono receiver, so ‘high-end’ audio isn’t really a realistic goal. Ultimately the best route is in fact deciding whether you like the sound.

[@BobAndersson]

Nice one. After watching this I think the next time I do a visual FM IF alignment I might try temporarily replacing the discriminator electrolytic with something about 1/100th the value so 1/100th the visual alignment frequency displacement - 47nF instead of 5uF in this instance. Any thoughts? As a matter of routine I've started replacing the electrolytic with a polyester cap anyway if space permits (for lonevity rather than any expectation of fidelity) so it is only one extra step after discriminator alignment. I got a bit lost on the FM bandwidth section though. I had always thought that the frequency deviation corresponded to the instantaneous voltage of the modulating signal. If that's true then overly restricting the bandwidth of the FM IF means that loud signals get distorted but frequency response, at least to a first approximation, doesn't change too much. But as I progress into my eighth decade my personal bandwidth gets more restricting and I'm more and more easily confused. 🤣

[@electronicsoldandnew]

I also thought I’d have to add a smallish cap to get a clean signal on the sweep, but found that the trace is quite clear without any cap. A small one would make the trace cleaner, definitely, and would have a negligible effect on the shift. As regards the bandwidth, I must admit that, while I’m now a poaching my 6th decade, I also get a little mixed up in my frequency vs time domains 😊 ultimately the important thing is that you get clear good audio, which is what I aim for. The bandwidth issue is one that I don’t follow too strictly on these 50s radios due to their rather limited use of the FM bandwidth as regards signal content in the transmission. Go for satisfied ears rather than pretty curves. It’ll always serve you well 😊

[@BobAndersson]

@@electronicsoldandnew I couldn't agree more about FM bandwidth. I sometimes use my Graetz Fantasia 622 to listen to classical music on FM but 90% of the time I use one of your v2 Bluetooth boards to listen to radio (Lush FM in California actually) via the Internet. The board allows the audio section of that radio (a push/pull output stage feeding two large elliptical drivers, a smaller midrange elliptical and a horn tweeter) to shine and every time I use it I send a "thank you" thought your way. 🙏

[@electronicsoldandnew]

👍

[@pybelleau]

What video editing are you using because it seems to do a very professional job ? Is it free ?

[@electronicsoldandnew]

I use Davinci Resolve, and yes, it is the free version.

[@bofor3948]

Nice to see the comparison of results using the different alignment methods. Think my next investment is a sweep gen as the results look worthwhile. BTW when you say you you shift the frequency to extend the upper end of the FM band to capture 101Mhz. Have you ever tried a 10MHz frequency shifter on the front end which can be switched on to change the range from 88MHz - 100MHz to 98Mhz - 110MHz to be able to listen upto the 108Mhz of modern radios? (Google - Nordmende Tannhauser 53-3D adaptation) The circuit boards can be made up to be removable in the same way as the BT boards and also supplied from the heater chain. Another switch is required or needs to be adapted as with the BT and there may be some loss of sensitivty and also possibly strong local stations on the lower band overlapping with the shifted frequencies when switched on. I am thinking of trying this on a BUSH VHF64 that I am about to restore (Will also reference your wonderful restoration of that model)

[@__Dude_]

I may be mistaken, but isn't the channel spacing on (European) FM 100kHz?

[@electronicsoldandnew]

Some countries use 100, while other use 200. At some point in the past they even used 50, so I’m not sure if it’s actually standardised.

[@renowden2010]

No problem this time with the motor IF not matching the receiver IF then.

[@electronicsoldandnew]

None at all 👍

[@jutukka]

Very nice work! Do you ever count hours spent on those radios? 🤫

[@electronicsoldandnew]

No, I don’t want to ever have to quantify it 😊 It is a hobby, after all.

[@jutukka]

@@electronicsoldandnew Well, your wife probably counts, so you can always ask her. 😂 Just kidding. (Not really, we both know it is true. 😜)

[@electronicsoldandnew]

It is true 😊 if I ever made this a profession, I’d let her do the costing and billing. She wouldn’t fail 😊

[@mackfisher4487]

Good job, so is this your new faveret radio

[@electronicsoldandnew]

Not yet … we’ll see how the cabinet works out 😊

[@pisotones2348]

Hi, Manuel. Your SDS1204X-E scope is begging for a FW update 😉

[@electronicsoldandnew]

I did one recently. Did another one get released?

[@pisotones2348]

@@electronicsoldandnew The blinking on/off switch when off is a feature not seen on those scopes for many moons now. Prehaps you should update the OS too!

[@electronicsoldandnew]

Good point. I’ll do that. That blinking has always irritated me.

[@pisotones2348]

@@electronicsoldandnew Nevermind. I've been investigating this issue and it seems to be related to the power supply which is not modifiable by either FW or OS updates. Sorry for the confusion! 🤭

[@electronicsoldandnew]

No problem 😌

[@muhammadrafique3903]

Nice video RAFIQUE MASTOI DG Khan Pakistan 🏝🇵🇰🇵🇰🇵🇰🇵🇰🇵🇰🇵🇰🇵🇰🇵🇰❤