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radionut
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Post subject: Fine tune condenser? Posted: Dec Fri 21, 2018 4:20 am |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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JnTX
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:28 am |
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Joined: Nov Tue 14, 2017 5:09 am Posts: 3574 Location: Austin, Texas
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A second set of plates for fine tuning is not uncommon on the communications receivers used by hams. Usually there is only one plate per section in those receivers so the ones in your radio look different then I have seen before. I think they are probably for the same purpose of allowing more precise tuning of short wave stations.
Jay
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:34 am |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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it also affects the broadcast band. There was no alignment info in riders so getting it right on is going to be tricky .
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pixellany
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:38 am |
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Joined: Jul Mon 26, 2010 8:30 pm Posts: 29651 Location: Annapolis, MD
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Tell us what happens mechanically when tuning. For example, is there just one tuning knob, or are there two?
_________________ -Mark "Voltage is fun to watch, but it's the CURRENT that does the work."
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:51 am |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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there are 2. One for each condenser. If your going through the dial towards 1600 and say it's not too sensitive ,if you turn the small set it brings in more stations. If your finding a weak station ,tweaking the small condenser brings the signal in better. Not ever seeing this set-up ,I've just been playing around with it and that is what I have discovered.
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pixellany
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:59 am |
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Joined: Jul Mon 26, 2010 8:30 pm Posts: 29651 Location: Annapolis, MD
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Model number??
My guess is that the smaller tuners are used to peak up the antenna and RF stages.
_________________ -Mark "Voltage is fun to watch, but it's the CURRENT that does the work."
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lorenz200w
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 5:05 am |
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Joined: Jan Mon 16, 2012 4:15 pm Posts: 7440 Location: Near Brandon, Iowa
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Appears to me to be a shortwave bandspread feature: the main tuning cap is used for gross tuning; the smaller cap rotor is used for fine tuning. The stators of the two caps are in parallel so the capacitance is additive. The 0-100 graduated scale is for logging the position of the fine tuning cap. Similar concept to what is used in the Hallicrafters S-38 entry-level receiver.
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thunderbird281
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 6:30 am |
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Joined: Feb Sat 06, 2016 1:47 am Posts: 3450 Location: La Mesa Califonia
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It's a nice option to have in all bands. If you were to monitor the AVC such as S-meter does you will see you can peak any station to best reception with the fine tuning capacitor.
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 11:54 am |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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pixellany
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 2:20 pm |
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Joined: Jul Mon 26, 2010 8:30 pm Posts: 29651 Location: Annapolis, MD
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Well, the schematic is no help.....
Note that there are three circuits tuned by the tuner: BC antenna transformer, RF (affects all bands), and oscillator (also all 3 bands). To understand what the smaller tuners do, we simply need to know which of the three circuit they are part of.
_________________ -Mark "Voltage is fun to watch, but it's the CURRENT that does the work."
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 2:31 pm |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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Yep,not much info there.No alignment info.Those small company radio manufacturers had very poor schematics.At least thas my experience...
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Wally58
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 2:32 pm |
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Joined: May Sat 12, 2012 1:33 pm Posts: 1743 Location: Rochester, NY.
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Is this the receiver?: http://www.nostalgiaair.org/pagesbymode ... 002957.pdf Is the 'fine-tune' variable capacitor linked to the dial pointer at all? Or is it possible that it is not a fine-tuning capacitor and is used to maximize, compensate or trim the antenna input (also used in many communications receivers)?
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 2:54 pm |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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Yes,thats it.It has its own pointer.Good thought there .May be an antenna trim.
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lorenz200w
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 4:15 pm |
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Joined: Jan Mon 16, 2012 4:15 pm Posts: 7440 Location: Near Brandon, Iowa
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radionut wrote: Yes,thats it.It has its own pointer.Good thought there .May be an antenna trim. It wouldn't be an antenna trimmer if it operates on both the oscillator and antenna sections of the tuning cap.
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radiotechnician
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 5:42 pm |
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Joined: Sep Thu 23, 2010 6:37 am Posts: 12437 Location: Powell River BC Canada
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The police and aviation bands are set by a trimmer according to the instructions, with a 3500 kHz signal. Given that they are in the 49 meter band, it could be the extra pointer is a band spread logging dial.
Other bands on the short wave dial are received by tuning within their shaded section.
That makes it difficult to dial in a station, that the user may need to monitor.
A way of doing it on radios with band spread, is to set the main pointer to the lower edge of the band shaded block, with the single pointer set to "0" Then the single pointer is tuned up until the station wanted is heard. Whatever number the pointer is set to is then logged. Later once the wanted station is heard, the user can two-hand the dials until the logged station is found at the number it should be, and the main dial is sweetened to rest exactly at the start of the band block.
That is how I used my band spread pre digital.
'""""
_________________ de VE7ASO VE7ZSO Amateur Radio Literacy Club. May we help you read better. Steve Dow ve7aso@rac.ca
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radionut
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 5:57 pm |
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Joined: Feb Thu 08, 2007 2:23 am Posts: 1072 Location: central Ohio 43062
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Wow,thanks for that info!! Quite a little rig here.When I got this radio someone had robbed the transformer and cut out all the speaker leads so it has been a little work to get this going.
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pixellany
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Post subject: Re: Fine tune condenser? Posted: Dec Fri 21, 2018 6:21 pm |
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Joined: Jul Mon 26, 2010 8:30 pm Posts: 29651 Location: Annapolis, MD
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with regard to the tuning question, can you check which part of the tuner is what? pixellany wrote: .....
Note that there are three circuits tuned by the tuner: BC antenna transformer, RF (affects all bands), and oscillator (also all 3 bands). To understand what the smaller tuners do, we simply need to know which of the three circuit they are part of.
_________________ -Mark "Voltage is fun to watch, but it's the CURRENT that does the work."
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radiotechnician
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Post subject: Re: Fine tune condenser? Posted: Dec Sat 22, 2018 10:08 am |
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Joined: Sep Thu 23, 2010 6:37 am Posts: 12437 Location: Powell River BC Canada
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Looking at the photo of the chassis, and reading the alignment instructions I concluded that the extra mesh gangs did adjust the oscillator. The wording seems to mean the rear gang is the oscillator, however touching the gang with a station playing will show this.(or the wiring could be traced.) If I were an Admiral collector, that set would one I would want to have. Admiral TV sets were one of my favorite brands, in the TV service days. A more detailed picture of how the rotors of the main and fine tuning gangs meshed with the stators would be nice. Attachment:
Admiral oscillator.JPG [ 26.03 KiB | Viewed 1920 times ]
_________________ de VE7ASO VE7ZSO Amateur Radio Literacy Club. May we help you read better. Steve Dow ve7aso@rac.ca
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azenithnut
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Post subject: Re: Fine tune condenser? Posted: Dec Sat 22, 2018 3:29 pm |
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Joined: Jan Mon 18, 2010 2:13 am Posts: 22114 Location: Dayton Ohio
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Very interesting radio. Unusual to have a bandspread feature in a tombstone.
Though I do have this tuning capacitor assembly which has the same feature. I have NO idea what radio it came out of.
The brand is "DeJong" De Adco Products --- Chicago, U. S. A.
Hard to make out the script... or maybe De Long?
Anyhow, it also has the bandspread outboard variable capacitors on the back of the main tuning capacitors.
-Steve
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dejongdial.jpg [ 92.26 KiB | Viewed 1900 times ]
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_________________ Radio Interests -Zenith -Sparton -Pre-War FM Consoles and floor models, the bigger, the better!
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majoco
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Post subject: Re: Fine tune condenser? Posted: Dec Sun 23, 2018 11:56 pm |
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Joined: Mar Mon 17, 2008 5:05 am Posts: 5532 Location: Ashhurst, New Zealand
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When the "Fine Tune" pointer is set to zero, what is the capacitor position? Totally meshed or fully open? On the highest frequency band it may not be possible to get the proper alignment if the capacitance of the "Fine Tuner" is too much - it may have to "guess and hope"! Set the "Fine Tune" to the other end of the scale and try again.
I have a Heathkit "Mohican" receiver where they specifically say "Set the Bandspread control to fully meshed" when setting the alignment - but even so it is very easy to get it wrong. The frequency range of the oscillator trimmer is so great that it is possible to get the oscillator on the wrong side injection. The best test is to use a digital radio to find the oscillator frequency and make sure of it's frequency - it's usually above the signal frequency. If you find that the band is deaf in the middle then you've got it wrong!
_________________ Cheers - Martin ZL2MC
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