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G8MNY > BEACON 05.03.06 19:03l 57 Lines 2556 Bytes #999 (0) @ EU
BID : 20113_GB7CIP
Read: GUEST
Subj: GB3VHF Beacon Measurement
Path: DB0FHN<DB0FOR<DB0SIF<DB0FHK<DB0LJ<DB0RES<DK0WUE<I0TVL<CX2SA<SV1CMG<
SP7MGD<ON0BEL<GB7CIP
Sent: 060305/1555Z @:GB7CIP.#32.GBR.EU #:20113 [Caterham] $:20113_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : BEACON@EU
By G8MNY (New Mar 06)
(8 Bit ASCII Graphics use code page 437 or 850)
Following the RSGB News item on this rebuilt beacon (well done that team), I
have repeated some tests on the beacon accuracy against my off air TV locked
standard while we still have accurate Analogue TV timebase signals (not
digital).
Using my digital PLL signal generator with its internal reference locked to TV
Syncs from the main Crystal Palace (or Croydon for Five) Analogue TV Tx.
(see my bul on "Off air lock for ref osc")
GB3VHF is currently on 144,430,000 Hz with this error..
Reference used BBC1 BBC2 ITV1 CH4 FIVE
Beacon readout ñ1Hz ñ1Hz +21Hz ñ1Hz +2Hz
That makes ITV1 & Five Tx low in line frequency when I tested.
Previous beacon measurements were much worse..
Date measured
Beacon Location Allocation 4/2000 6/2001 1/2006
GB3VHF Wrotham beacon from Kent on 144.430 -800 -1033 -390 Hz.
GB3ANG Scottish "Angus" beacon on 144.453 ? -400 +1900 Hz.
ON4VHF Belgium beacon allocated 144.415 ? +500 +1080 Hz.
F5XM The French beacon allocated 144.425 ? +170 Spot on 0 Hz.
THE SETUP I USED MEASURE THE BEACON FREQUENCY
UHF Stray 2M
\³/ \³/ \³/
ÚÄÁÄÄÄ¿ 15625.00000Hz ÚÄÄÄÄÄÄÄÄÄÄÄÁÄÄ¿ ÚÄÄÄÁÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿
³ VCR ÃÄÄÄÄÄÄÄ>ÄÄÄÄÄÄÄ´ PLL SIG GEN ³ ³ VHF ÃÄÄÄ>ÄÄ´ AF Freq ³
³TUNER³ Video ³ locked to TV ³ ³ AM Rx ³ 1KHz ³ Counter ³
ÀÄÄÄÄÄÙ ³ 144429000.0 ³ ÀÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÙ
BBC1/2 ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ 1000Hz
To measure beacons etc, it is no good zero beating as you can't tell were you
are as you approach zero beat. So I set my TV timebase locked signal generator
to be 1KHz low, this then produces a 1KHz audio beat note with my Rx in AM. I
adjust the Sig gen level to be about the same in th Rx as the beacon. Then I
measure the AF on a comms counter. The new beacon data format does not allow
much time to do really accurate measurements (reading say for 10s). For weak
beacons an AF osc can be compared by ear & this method is OK to a few 10s Hz.
This rebuilt beacon is SPOT on now, & zero beating a rig (dummy load) to it &
calibrating your frequency counter to that will result in a only a few Hz error
(say ñ10Hz) at 2M.
Why don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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