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Old 7th Nov 2021, 9:23 am   #81
murphyv310
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi.
I've now dispensed with the 0.01uf cap and added a stopper resistor of 27k instead and padded the output to ground with 150k this has really improved fidelity. I have also added to the description on the video. Hope this helps.
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Old 7th Nov 2021, 9:56 am   #82
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Thanks also for your answer regarding the 50V output capacitor.

I wouldn't ask removing the video, but I would prefer the following:
- cutting the opposite dial direction as this is already fixed
- say that the "pops" are normal due to the nature of the PLL chip being silghtly out of tune (equivalent to static noise on an analog tuner)
- mention the background noise but explain we're investigating and that it is not present on my transistor radio.
- not saying that people could be disappointed, as it is already quite an improvement for AM radios. I don't know how many AM channels you still have (I heard the BBC would stop AM broadcasts soon), but here in France we only have one channel (RTL), so the FM conversion is always much preferred.
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Old 7th Nov 2021, 10:22 am   #83
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi David.
I've no idea how to cut parts out of the actual video.
I'll delete the full thing.
Here I have 7 receivable stations on MW. BBC have no plans to stop BBC Scotland on 810 due to reception difficulties in the Highland District.
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Old 7th Nov 2021, 1:43 pm   #84
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi David it would be worth wile updating the schematic on your site of Trevors modification . Hi Trevor great job you have done and thanks for sharing it with us I will do your modification and report back . Here in Sunderland I am getting 12 stations with a 3 foot piece of wire the same amount of stations I can get in the car
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Old 7th Nov 2021, 2:05 pm   #85
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Out of interest hear is the stations I can receive in ascending order from 88.5 MHZ to 107 MHZ Radio 2 3 4 Radio Newcastle Metro Radio Smooth Radio Radio 1 Classic FM Heart Radio Sun FM Capitol Radio Spark Radio
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Old 7th Nov 2021, 3:37 pm   #86
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Trevor's mod has been added to the description.
Next production run (if any) will incorporate those two resistors.

Concerning the background noise: with further tests using my transistor radio, I could hear it when tuning 100KHz after a station. Tuning 100KHz back and forth made the background noise disappear when tuned to the exact frequency, and come back 100KHz after. As the module tunes by 100KHz increments, this isn't really an issue, but rather a matter of being used to tune the module right, which isn't hard at all.

Let me know if you still have the background noise even when tuning. I can verify where I tune because I added a small LCD module to my radio, where the tuned frequency is shown. However, this adds audible beeps due to the data being transferred, but this is only for debuging purposes.
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Old 7th Nov 2021, 5:00 pm   #87
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi David Please keep up the production run as you are providing an excellent service and is I have said in previous posts this is getting radios to work and not been display pieces or in an attic gathering dust
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Old 7th Nov 2021, 6:29 pm   #88
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi Just to confirm that Trevors modification works on my set as well
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Old 7th Nov 2021, 6:33 pm   #89
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi.
I'm just uploading a new video with the improvement in audio quality quite easily heard. Still some background noise heard on occasions but a big improvement.
I'll upload a circuit of the additional parts.
The values are not critical, they add a load to the output and reduce the impedance slightly, enough to improve fidelity. The set now sounds as good as it did with the existing tuner etc.

NOTE, the 1.5nf may not be needed in all sets.

https://youtu.be/8X0Iv3gsW64
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Old 8th Nov 2021, 10:33 pm   #90
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi Trevor, nice and interesting videos. What's the purpose of the 1.5nF capacitor ? Can the mod use a 1nF or a 2.2nF capacitor instead (as these two values are more common) ?
Also, I suppose that your mod concerns amplifiers where you feed the volume pot feeding the preamp tube. What if there is some tone control circuitry between ?
It's important to mention whether your mod can be added on every set, or if it only concerns some specific designs.
I must admit that I have converted over 150 radios so far, and never felt that the sound was bad except for low grade sets with a smaller speaker. In fact, when used on larger sets with speakers of at least 7" diameter, and especially with sets having a tweeter, the sound was really impressive. I never felt that any tone correction was required (hence the question).
I'll try it on one of those sets by the way, and keep you informed.

Oh, forgot to say: as a little thank you for your participation with this mod, I'll send you a module free of charge with the latest software.
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Last edited by david winter; 8th Nov 2021 at 10:42 pm.
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Old 9th Nov 2021, 11:24 am   #91
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Default Re: My FM converter for tube radios using the dial and tube amplifier

That is very kind of you David, thank you very much.
Because the output of the module is low impedance putting a small cap on the output really makes little difference to the equalisation. The resistor network increases the impedance a little and makes tone correction more effective and easier to do.
This set has a 5 inch speaker of reasonable quality. Adding just the resistor network on this set restored the tone control effectiveness. Being fair I've lost a lot of my HF due to being a little deaf so it must have been very tippy to younger ears. The value of cap is not critical and personally I'd not add it to the circuit, just as an additional circuit if there is problems on some sets. I'd probably just add a 47k in series with the AF output on the board and leave it at that.
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Old 21st Nov 2021, 9:35 pm   #92
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Default Re: My FM converter for tube radios using the dial and tube amplifier

I just ordered eight of these. I hope the version sent to the USA works with the FM here.... If I like it, I'll also be installing one in my HMV468, which will be going back to Europe, perhaps next year (to our flat in Vilnius, where the clock will keep time).
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Old 21st Nov 2021, 10:19 pm   #93
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Hi.
I've received the modified module from David but I'm up to my ears in the 2807 and other projects so once cleared I'll install it in a Pye radio I have and report back.
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Old 21st Nov 2021, 10:41 pm   #94
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Quote:
Originally Posted by FStephenMasek View Post
I just ordered eight of these. I hope the version sent to the USA works with the FM here.... If I like it, I'll also be installing one in my HMV468, which will be going back to Europe, perhaps next year (to our flat in Vilnius, where the clock will keep time).
Hi Stephen please let us know how many stations you receive
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Old 21st Nov 2021, 10:42 pm   #95
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Quote:
Originally Posted by murphyv310 View Post
Hi.
I've received the modified module from David but I'm up to my ears in the 2807 and other projects so once cleared I'll install it in a Pye radio I have and report back.
Hi Trevor looking forward to see your findings
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Old 21st Nov 2021, 10:57 pm   #96
david winter
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Default Re: My FM converter for tube radios using the dial and tube amplifier

Quote:
Originally Posted by FStephenMasek View Post
I just ordered eight of these. I hope the version sent to the USA works with the FM here.... If I like it, I'll also be installing one in my HMV468, which will be going back to Europe, perhaps next year (to our flat in Vilnius, where the clock will keep time).
Thanks for your order. I will ship tomorrow.
Don't worry, your modules will definitely work in the USA, and will of course come with the latest firmware. Don't forget to add Trevor's mod (2 resistors as explained on the page).

I hope you enjoy them !
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Old 22nd Nov 2021, 3:24 am   #97
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Default Re: My FM converter for tube radios using the dial and tube amplifier

I will post information and photos of several radios.

We have full AM and FM dials in southern California, with Chinese and Vietnamese music on AM stations. At night, I can even get AM660 in Window Rock, Arizona, which plays Navajo (Where else can you hear Navajo?) Country, and Rock music!
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Old 1st Dec 2021, 3:17 am   #98
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Default Re: My FM converter for tube radios using the dial and tube amplifier

I received the eight I ordered today, and expect to have the first one installed in a Capehart Panamuse which had the now useless pre-WWII FM band. I also have six 120 to 6.3 volt transformers to allow installation in radios with 2.5 volt filament circuits. The small size of the modules will be a significant factor in ease of installation.
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Old 1st Dec 2021, 7:55 am   #99
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Default Re: My FM converter for tube radios using the dial and tube amplifier

It would be interesting to see your custom AM/FM switch. You need a DPDT switch (one section for the tuning cap, the other for the audio). You may need to adjust a little bit around the frequency changer to compensate the capacitance added by the wires / switch. Use the local oscillator section of the tuning capacitor to make it easier.
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Old 2nd Dec 2021, 6:13 pm   #100
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Default Re: My FM converter for tube radios using the dial and tube amplifier

It works on the Capehart Panamuse. It sounds great, with the two original speakers and the tweeter and inductor & capacitor crossover I added.

I connected all three of the original pre-war FM tuning gang sections together (orange wire).

I connected the module antenna terminal to one of the original FM doublet terminals on the back of the chassis.

The tiny switch is difficult to use. I destroyed one module trying to press the switch. A larger switch with a light to indicate when it has been pressed would be a great improvement.

I mounted it with silicone caulk.
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