Silva S15 VHF - Problems

[DMac]

Hi,

I've got a Silva S15 VHF and am having some problems receiving calls on it. First assumption was the antenna connection on the back as we had to do this ourselves when we took delivery of the boat. Last week we took off the connector and redid it but if anything the problem is worse. Symptoms include not receiving any of the transmission or in some cases missing the first few seconds and then it picks it up. The Squelch setting seems to be OK, tried turning it right down and problem still shows up. It appears transmission from the radio is working OK.

At this point considering taking the connector off again and redoing it but not sure what to do differently!!! In terms of putting the connector on the cable we folded the shielding back over the outer cover, screwed that into the connector and then soldered the inner core. Any advice or tips on the best way to make this connection would be appreciated.

Coincidentally we've now been told by the Irish Regulator (ComReg) that they have been notified that the S15 is not compliant with EU regulations/standards - some tests being done in Norway apparently. Because of these they are refusing to issue the license at the moment.... Anybody know any more about this ? I guess if its true then this will not just be a problem in Ireland. Going to talk to them again tomorrow to see what exactly the problem is.

Regards,

Declan.

<hr width=100% size=1>

 

[William_H]

Ideally what you need is a VSWR meter. Voltage Standing Wave Ratio Meter This is a device which connects between the set and the antenna cable and measures how good your antenna and cable is. They used to be very popular with CB enthusiasts and any ham radio operator will have one. Its a box about 20 cms long with 2 coax connectors on the ends or back and one or 2 meters. It is used on transmit and measures the power going out to the antenna from the transmitter and with the flick of the switch or on the other meter the power being returned. A good antenna and cabling will give about 5% returned while a bad connection will give 100% returned. Tandy radio Shack RS etc. used to sell them quite cheaply but I havn't seen them lately. If you can't find one some radios have a similar circuit built in which will; indicate transmit power by a light or meter and you could compare results with antenna connected and not connected. An open circuit or short circuit have virtually the same effect while a good antenna should give the right indication. If an antenna is good at transmitting it will be good for receive assuming you don't have a serious local interference problem.(turn all other eqipment off) While listening to stations you could substitute a piece of wire about 60 cms long pushed into the hole where the connector goes into the radio if you find this works better than your antenna obviously you have a problem. If you want I can email you a description of how to build anemergency VHF antenna which may prove as a substitute if you have an antenna problem. Make sure you have set the squelch properly. It is a circuit which kills the receiver until a signal is received. The adjustment sets the level of signal which will open the squelch circuit. For difficult conditions it should be set so that background noise is heard so that the weakest signal will also be heard. I get irritated when people refer to the background noise as squelch. The word squelch in radios refers to the trick of killing (squelching ) the background noise. Just a few thoughts which may or may not help regards will

<hr width=100% size=1>

 

[DMac]

Thanks Will,

I'll see if I can get my hands on one of those meters. If you have that info on emergency VHF antenna I would be interested.

Rgds,

Declan.

<hr width=100% size=1>

 

[DJE]

I would be interested to hear more about the S15 failing compliance tests. I have had one for about a year and it is fine as a normal VHF but the DSC side does seem to have some strange habits. It fails to log calls some times and recently it transmitted my position for no apparent reason. See my post "Baffled by DSC" on Scuttlebutt on 29th July. Do you have a Navtex connected? and if so have you found any way of shutting down the incoming message alarm?

<hr width=100% size=1>Better to keep one's mouth shut and be considered a fool than open it and remove all possible doubt.

 

[steve_cronin]

You say that the transmission is working OK. How did you arrive at this conclusion?

A SWR meter used for CB (27mhz) isn't entirely suitable for 156mHz VHF but theyt are made. I have one which is available for loan against an RNLI donation! Anyway, the SWR meter will only show the power of your transmission and wether or not the aerial is tuned corectly for this and not allowing signal to "bounce back" and damage the output stage transistors. Any receiver will receive on a vaguely matched bit of old wire. A badly matched antenna shouldn't cause the effect you describe of missing the first part of a transmission. I would have thought that your trouble lies either with the PTT switching or the squelch.

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[fd_211]

I've had similar problems with the Silva S15.
It appears that the initial few seconds of the recieved signal doesn't come through.
I had a handheld VHF and could pick up the transmission from the coastguard on that but not on the Silva S15.
Squelch setting ...etc were all set up ok.
The coast guard antenna was situated 3 miles away.
Tranmission on the other hand is clear (according to any radio checks I've done so far).

Anybody else have a similar problem?


<hr width=100% size=1>

 

[Oldhand]

Sounds like you have a very slow acting squelch circuit.

<hr width=100% size=1>

 

[bruce]

the 1:1 swr on cb is equal to a 3:1 on vhf freq on the cb meter, as for the emergency antenna, take a length of coax, peal back about 18" of shielding, tie string on center wire and hold up. instant antenna. let shield dangle, will end up with a 'T' looking thing.

<hr width=100% size=1>

 

[bruce]

perhaps the power in the radio receiving circuit may not be enough to trip the relay to let signal into the amp section of the radio. sounds like a trip to the radio shop.

<hr width=100% size=1>