Riittävä etäisyys rigiin, mutta se ei paljoa auta jos tarvitsee sen kännyn esim gprs qsoon siinä samalla pöydällä. Niinkuin oli mulla joskus. Eli en ole sittemmin käyttänyt nettilusteria.
Elecrafti listalta löytyi OH2ZAZ posti:
Elecraft] Re: [TenTec] RFI from GSM phone into 705 mike?
from [Arjen Raateland] [Bookmark Link][Original]
To: <elecraft>
Subject: [Elecraft] Re: [TenTec] RFI from GSM phone into 705 mike?
From: Arjen Raateland <Arjen>
Date: Sat, 26 Aug 2000 19:52:17 +0300
Arjen Raateland wrote:
> I just noticed that my Ten-Tec 705 desk mike suffers from RFI whenever a
> GSM phone is active within ca. 3 m. I don't have a GSM phone myself, so
> I hadn't noticed this before.
>
> When VOX is used, the rig's TX will come on with full power; when PTT is
> used, the GSM phone also causes a microphone signal more than big enough
> for full output. As detected on a second RX the resulting audio is
> typical of GSM phone interference.
I haven't been on-line yet since sending off the above, so I haven't
read replies if any, but in the mean time I have succeeded in making the
mike quite a bit less sensitive to the GSM signal.
First I slipped a single large ferrite bead type FB43-801 on the white
(af), red (+) and black (gnd) wires from the microphone cable near to
the PCB. This helped nicely, as the RFI free distance was more than
halved from 3 m to 1 m.
Next I dug up a not too big clamp-on choke and added that over the
microphone cable inside the mike stand. It does take up fairly much
space, but I don't use a battery inside the stand anyway.
Then I unsoldered the twisted wires to the microphone element close to
the PCB and pulled them twice through a longish ferrite bead type
FB77-6301 (5 mm hole) before resoldering them. (Fortunately I had used
teflon insulated wire, so it didn't become a mess.)
The sensitivity to the GSM signal is now even better (say half a meter).
I think that it might also be wise to add a ferrite bead with a few
turns in the af signal line on the jumper block inside the K2
transceiver itself. I found that the TX is keyed by a close-in GSM
signal even when the 705 mic's pre-amp isn't on (while using VOX mode on
the K2).
I did NOT test for RFI rattle on the modulation itself during normal use
of the transmitter when a GSM phone is operated nearby. I just tested
how far away the GSM phone needed to be to not activate the the VOX.
I'm afraid there won't be any more testing now as I had to borrow a GSM
phone to do the tests and even though ringing is enough the test for
RFI, the phone has to be on, of course. I managed to lock up one GSM
phone by entering the wrong PIN code thrice, which is a big boo, boo
To re-open it, forms need to be filled in triplicate, or so it seems as
the phone is job-related ....
Anybody using a microphone preamp inside the K2 transceiver could do
worse than adding ferrite beads already during installation. One could
probably even slip small beads over the jumper block pins.
BTW, my current setup: K2 and Ten-Tec desk mike sit only a few meters
away from the Hustler whip antenna (20 m) on my balcony, but that hasn't
caused any problems. However, a GSM signal of rather less power is able
to cause a good amount of RFI.
73,
- --
Arjen Raateland
OH2ZAZ
AX.25: OH2ZAZ@OH2RBI.FIN.EU