R:190723/0833Z 14403@LU1DNS.SA.BA.AR.SOAM LinBPQ6.0.17
R:190723/0833Z 10814@LU3WAM.CHU.ARG.SOAM LinBPQ6.0.17
R:190723/0833Z 8685@PY2BIL.SP.BRA.SOAM LinBPQ6.0.18
R:190723/0832Z 4933@CT1ENI.CT1ENI.CTST.PRT.EU LinBPQ6.0.18
R:190723/0830Z @:LU4ECL.LP.BA.ARG.SOAM #:5824 [La Plata] FBB7.0.8-beta2 R:190723/0828Z @:GB7CIP.#32.GBR.EURO #:13247 [Caterham Surrey GBR]

From: G8MNY@GB7CIP.#32.GBR.EURO
To : HIFI@WW

By G8MNY (Updated Jan 09)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font) ┌─────────────────────────────────────────────────────────────────────────────┐ │┌───┐ ┌──────────────────────────────────────────────┐ │ │└───┘ o O O O │Quartz lock Stereo RDS ch TUNE│() /~~~\ │ │ │ ┌─┐ .. 3 | ┌─┐ ┌─┐ ┌─┐ ┌─┐26 MODE│ | | │ │ [_][_][_] [__]│ │││ .... 2 │ │ │ │ ├─┤ │ │ Auto│ ▐ ▌│ │ │ │││││ ......1 | └─┘ |*└─┘ └─┘ Man │ | | │ │ │ signal FM MHz Lock│ \___/ │ │ ┌───┬───┐┌───┐└──────────────────────────────────────────────┘[ ] │ │ └───┴───┘└───┘<][ 1][ 2][ 3][ 4][ 5][ 6][ 7][ 8][ 9][ 0][10][> │ └─────────────────────────────────────────────────────────────────────────────┘ I was given a faulty one of these tuners, it covers LW, MW & Band 2 with RDS, & its has 39 memories. I have now got it all going OK.

CLEVER AUTO IF WIDTH
It has an unusual feature regarding the automatic FM IF filter width selection I have not seen before. If the station is strong enough, it uses the wider low distortion IF (300kHz), unless there is a nearby carrier. It decides this by tuning ±100kHz first with the narrow filter (180kHz) & if there is a signal marking the spectrum graphic display with a bar │ to the left or right of the main carrier & then it uses the narrow filter.

PSEUDO SPECTRUM GRAPHIC
The Spectrum Graphics shows the IF bandwidth selected....

IDEAL BAD BAD BAD IDEAL
STRONG LF HF ± LF HF ± BUT WEAK
NO QRM Sig QRM QRM QRM QRM QRM QRM NO QRM Sig
┌───┐ .. 3 ┌───┐ ┌───┐ ┌───┐ ┌─┐ ┌─┐ ┌─┐ ┌─┐
│ │ │ .... 2 │ │ │ │ │ │ │ │ │ │││ │││ │││ │││
│ │ │......1 │││ │ │ │││ │││││ ││││ ││││ │││││ │││......1
WIDE MANUALLY FORCED INTO WIDE NARROW FILTER MODE SELECTED

I wonder if anyone has any information, tips, do's & don'ts etc. for this Rx?

AM ┼┬───────────────┐
It had no AM pickup ┼┤ VHF TUNER │
loop aerial, so I am │└───────────────┘
using a large loop from │ ┌───────┐
6m of wire, (about 10uH) │hf│( ) ( )│hf
& I tracked the series │MW│ │LW
LW & MW aerial & Osc coils │lf│( ) ( )│lf
coils to best match this. │ └───────┘
│
│ ┌──┐
│ │()│
│ AF └──┘
│ Notch ┌──┐
│Filters│()│
│______ └──┘_______
NO MAINS SWITCH!
As with many modern items there is NO MAINS SWITCH, the standby switch only really powers off the display.

Much of the power consumption on my UK mains @ 245V 50Hz is due to the large over run mains transformer (for 2x 110V 60Hz?) & gets hot even on standby with little load, as does the plastic power supply regulator transistors when on.

POWER MODIFICATION
I modified the mains circuit (the large empty PCB with the transformer was ideal) with a 2W 1k resistor in series with the mains neutral, & mounted it well above PCB, I also tuned the mains transformer to 50Hz with a mains 0u15
X type Cap for minimum mains current (PF=1.0).
___________
Live────────┬──┐ ... │ Cooler │_____Rx
│ )││( │ Regulator │
245V 0u15=== )││( │Transistors│
│ )││(... ~~~~~~~~~~~
Neutral──1k───┴──┘ Cooler
2W Transformer

The result was a much cooler transformer all the time & cooler power supply regulators, & hence less power wastage despite adding the 2W resistor. The transformer voltage now has 230V on standby (2W consumed) & 220V when on (5W), there is enough power supply headroom for the cooler running regulators OK, but the display is very slightly dimmer due to the directly heated fillements. (longer lifetime?)

HUM
I have done this sort of thing before on another FM Rx, but that case is was due to acoustic & strong stray magnetic flux leakage hum from the super saturated transformer causing problems. Again adding an series R reduced both these completely.


Any feedback would be greatly appreciated.


Y don't U send an interesting bul?

73 de John G8MNY @ GB7CIP.



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