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Hello radio heads. I restore a lot of preamps and power amps, but I lack the RF equipment to do tuner work. I have a tuner/preamp I got from my father-in-laws girlfriend (a Mitsubishi DA-C20), and have gone through all of the analog sections, but the tuner is weak. I only get 3 stations well, and I should get a few dozen. Can anyone point me in the right direction on what to check? Thanks!
If so, the tuner has a problem.
Skeptical Measurer & Audio Scrounger
So was reception poor on AM and FM? What was the FM antenna? I assume there is an AM ferrite bar antenna. Finally where is it? In a house, apartment building? Describe the structure briefly. Metal buildings are bad.
I am located in my garage, and for testing I just use a simple dipole. Other tuners with the same setup, as well as a boombox with a single mast, get better reception.
Gotcha, sounds like something needs attention.
Hornlover, got a Mitsubishi DA-C20 pre-amp from KPFA yard sale back in fall '04. Great fidelity on both AM-n-FM(phono pre-amp is the b-o-m-b bay-bee). Sensitivity is great, with selectivity on FM benefiting from I.F. Band being in narrow mode. Just give your tuner section a simple dirty alignment, utilizing your tuning capacitor's alignment screws & peaking your s-meter. In conjunction with carefully adjusting your AM antenna's tuning slug. That should get you back into dx-mode. 73s para Sactown
I would like to get Capitol Public Radio KXJZ on 88.9 out of Sacramento, or one of its repeaters, KXPR at 91.7 out of Sonora. The only classical stations that I can get. They come in fine on the other radios (and cars), but not on this unit :(
Hornblower, just checked FM reception on DA-C20. Outdoor Winegard antenna's 75 ohm feed connected to 300 ohm input (for convenience), with IF BAND on narrow. KXPR, 88.9 Mhz from near-by Walnut Grove tower, pegged s-meter; Groveland's KXSR, 91.7 Mhz from roughly 85 miles away, registered a battered-but-readable 3 on s-meter. There is strong local interference from El Camino High's KYDS on 91.5 Mhz, & KXSR's reception would be muted if in IF WIDE mode. Selectivity, unfortunately, isn't a stock DA-C20's strong point. Now fidelity-n-sensitivity, OTOH, ... 73s para Sactown
Do I read this right? 75ohm downlink to a 300ohm INPUT?
Terrible impedance mis-match.
At least get a Balun to fix the impedance issue.
I made a 300ohm 'twinlead' antenna which is on a 'rotor' in the ceiling of my garage. AT THE Antenna is a balun. Down to the RADIO is 75ohm which screws into the antenna input.
Good results for a table radio (Tivoli #1) even though I live in a depression (the house, not ME) which is 40+ miles NORTH of SanDiego and thus well South of Orange county as well as impossibly far from LA. Yet, I do get some of the Mt Wilson FM feeds.
Too much is never enough
Pictureguy, connection of 75 ohm antenna feed to 300 ohm input was done, as previously stated, for convenience's sake. Yet, as noted, reception was still commendable. BTW, thanks for remindin' moi that DA-C20's interior balun was removed, so antenna feed is direct wired to 300 ohm input terminals. Having that stock balun in place might explain Hornblower's attenuated reception problem. 73s para Sactown
purportedly that unit has a great tuner section-
Having said this- a tuner is a bit like a tone arm with a mediocre cartridge - event the best tuner w/o a good antenna will not perform well -
That is not to say that as parts age- and the values drift may not also be part of the problem-
Tuner info may offer some help, otherwise I must defer to those who are more technically competent.
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