Anyone know a good mod to give the clarifier more range? I have a crystal to take it 35 to 40 but the clarifier needs a tad more range, and yes I know about the pots inside to adjust and yes I know that crystals drift with age....
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1976 midland 13 895 clarifier
- Thread starter demco satelite
- Start date
I had one years ago I think we lifted one end of the varactor diode and put another in series with it to get more range.
You could buy super slider diodes at every CB shop back then.
You have already adjusted the two vr's for widest range, yes?
73
Jeff
You could buy super slider diodes at every CB shop back then.
You have already adjusted the two vr's for widest range, yes?
73
Jeff
You can try adding a 5.6uH rf choke in series with the varactor or try an NTE614 varactor or a combination of the two.
Chokes like these:
Lot of 5.6uH Nytronics "WEE-DUCTOR" Axial Fixed Inductor RF Choke | eBay
Find many great new & used options and get the best deals for Lot of 5.6uH Nytronics "WEE-DUCTOR" Axial Fixed Inductor RF Choke at the best online prices at eBay! Free shipping for many products!
www.ebay.com
I put these in my watch file on ebayYou can try adding a 5.6uH rf choke in series with the varactor or try an NTE614 varactor or a combination of the two.
Chokes like these:
Lot of 5.6uH Nytronics "WEE-DUCTOR" Axial Fixed Inductor RF Choke | eBay
Find many great new & used options and get the best deals for Lot of 5.6uH Nytronics "WEE-DUCTOR" Axial Fixed Inductor RF Choke at the best online prices at eBay! Free shipping for many products!www.ebay.com
I looked at the schematic for this and it is way more complicated than the radios of the past 25 years. For a 50 year old radio like this I would probably want to start by checking the resistors in the clarifier circuit as a minimum first step to get to were you want to be. That would be R68, R69, R70, R71, R72, R73, R74 and R75. One or more may well be out of tolerance at this point in time. VR4, VR5 and VR6 should be cleaned with a good contact cleaner or replaced. This radio already has a 10uH (L1) RF choke in series with the Varactor D23. If you only need a little more slide, I would try the NTE614 next because it has a little broader tuning range the 1S2688. If that still does not get you to where you want to be I would next add more inductance to the Varactor. 15-18uH at the L1 position might work. Every component in this circuit affects tuning by the clarifier circuit. You will get to point to where you likely have the "wheels" fall off the wagon so to speak where more slide is unobtainable. Also another important consideration is to check the channel (at least one in every synthesis group) by channel frequency deviation of the radio from center. This radio synthesizes two crystals to get the desired frequency and when you get one or both out of tolerance, you can get a totally out of range or skewed channel frequency either up or down. You also have to consider the 7.8025MHz (X11) oscillator circuit which is used on all channels. I am seeing the problem of out of tolerance crystals more and more from these older radios and it is a problem that will get worse as time marches on. When you synthesize 3 of these old crystals together the problem greatly compounds. A proper alignment is also an important factor in the big picture.
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