5th May 2020, 2:49 pm | #141 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,579
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Re: Wet 1969 ITT-KB junior battery radio
Hi
I did a few checks with the signal generator and with reference to the pic in post #140 I connected the RF signal generator to pins D and E and the oscilloscope to the tuned winding pins A and C. I set the signal generator to around 450kHz. Looking at the sinewave on the 'scope and varying the frequency around 450kHz I noticed an increase to maximum amplitude at resonance. Resonance is not that sharp but is clearly noticeable. Altering the ferrite adjustment screw moves the resonant frequency as expected. I used the second channel (with no input) on the 'scope to place the horizontal trace at the peaks of channel 1's signal to assist in finding the point of resonance as it's not easy to see as the sinewave is opening and compressing as the frequency is altered. Having a fixed bright line marker makes it easier to see when the peak occurs. I found that resonance was about 452kHz though I should use the frequency counter to prove this. I also similarly tested a TOKO IFT from a later Roberts radio. That had a much sharper peak than the one in the ITT. Resonance occured around 455KHz. I'll have a look at the BFO circuit when time permits. My assumption is if it's used closely coupled to a radio with the same IF there should be a heterodyne effect, perhaps whistles/silence if the test IFT is adjusted around the same frequency as the radio's IF. If this proves to be the case, then resonance is occuring and the IFT should be fit for service. Regards, Symon Last edited by Philips210; 5th May 2020 at 2:59 pm. Reason: Additional info |
6th May 2020, 2:08 pm | #142 | ||
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
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Re: Wet 1969 ITT-KB junior battery radio
Quote:
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9th May 2020, 11:57 am | #143 |
Hexode
Join Date: Nov 2009
Location: Chertsey, Surrey, UK.
Posts: 456
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Re: Wet 1969 ITT-KB junior battery radio
I have bort a new soldering iron tip and tip restorer, just waiting on the post
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