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Weak reception

128.115.190.40
Posted on April 29, 2016 at 08:23:25
Hornlover
Manufacturer

Posts: 2529
Joined: March 8, 2002
 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!

 

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RE: Weak reception, posted on April 29, 2016 at 08:39:44
6bq5
Audiophile

Posts: 4391
Location: SF Bay
Joined: August 16, 2001
 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.



Happy Listening

 

RE: Weak reception, posted on April 29, 2016 at 13:17:06
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 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.

ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Weak reception, posted on April 29, 2016 at 14:22:36
Hornlover
Manufacturer

Posts: 2529
Joined: March 8, 2002
 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.

 

Do the other FM devices perform better in the garage?, posted on April 30, 2016 at 04:17:58
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 If so, the tuner has a problem.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: Weak reception, posted on April 30, 2016 at 19:38:51
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Gotcha, sounds like something needs attention.

ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: Weak reception, posted on May 1, 2016 at 07:41:27
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 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

 

RE: Weak reception, posted on May 2, 2016 at 08:48:39
Hornlover
Manufacturer

Posts: 2529
Joined: March 8, 2002
 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 :(

 

RE: Weak reception, posted on May 2, 2016 at 10:20:50
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 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

 

RE: Weak reception, posted on May 2, 2016 at 10:43:47
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 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

 

RE: Weak reception, posted on May 2, 2016 at 12:19:01
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 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

 

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