Top Loading

[Buckskinner33]

Has anyone ever top loaded a scanner before?

Top loading is a term I heard of when you have your scanner to close to a tranciever and it tends to de-sence the scanner.

I usualy have my scanner near by my handheld (2.5 watt output) or in my truck (45 watts output)

Beside the obvious answer of not having the scanner on while transmitting...Is there anything else I can do to protect the reciever?

 

[K5MAR]

That would be overloading. :lol: I can't say about your particular scanner, but I currently run a BC-780 in my truck, along with my 50 watt (nominal) ham gear and two 100 watt Moto rigs (VHF & UHF). Haven't had any problems with the scanner, other than desense and sometimes feedback.

Mark S.

 

[Buckskinner33]

That would be overloading. :lol: I can't say about your particular scanner, but I currently run a BC-780 in my truck, along with my 50 watt (nominal) ham gear and two 100 watt Moto rigs (VHF & UHF). Haven't had any problems with the scanner, other than desense and sometimes feedback.

Mark S.

Ok ... But are you monitoring the ham bands on your scanner while talking on you mobile rigs?

Because thats what Im doing.

Oh, BTW, Its a RS pro-95 scanner and a Motorola MTS-8250 Tranciever (Trunkated)

 

[Al42]

Ok ... But are you monitoring the ham bands on your scanner while talking on you mobile rigs?

Because thats what Im doing.

Oh, BTW, Its a RS pro-95 scanner and a Motorola MTS-8250 Tranciever (Trunkated)

Two different things here:

1) If there are protection diodes at the antenna jack of the scanner, it doesn't matter whether the scanner is on or off (unless the diodes are biased) or, if on, what band it's tuned to. If you pump enough power into the antenna jack, the diodes will "protect" the scanner - by shorting permanently. While diodes are cheaper than a good MOSFET transistor, unless you're good with a microscope the scanner still has to go back for repair.

2) If the scanner design is just the least bit skimpy, the front end will go at a signal level just under one that will destroy the diodes (assuming there are protection diodes in an el cheapo scanner) and it's most sensitive on the band it's tuned to.

Bottom line is, for best protection, turn the scanner off and disconnect the antenna in a high-RF environment. Wear a belt and suspenders. Wear rubbers over your boots, in case a boot springs a leak.

Or not.

 

[K5MAR]

Ok ... But are you monitoring the ham bands on your scanner while talking on you mobile rigs?

Because thats what Im doing.

Oh, BTW, Its a RS pro-95 scanner and a Motorola MTS-8250 Tranciever (Trunkated)

No, but I am monitoring the 150 and 450-460 bands on my scanner while talking on my 100 watt Motos on the 150 and 450-460 bands, as well as on the 2m and 70cm bands on my ham rigs.

I can't say about the construction of the Pro-95, but as a general rule, handhelds are more susceptable to overload and desense, simply because there isn't as much room in the smaller case for better filters. As for actually destroying the scanner, I haven't seen that happen, although I have heard anecdotal evidence.

Mark S.

 

[Buckskinner33]

Two different things here:

1) If there are protection diodes at the antenna jack of the scanner, it doesn't matter whether the scanner is on or off (unless the diodes are biased) or, if on, what band it's tuned to. If you pump enough power into the antenna jack, the diodes will "protect" the scanner - by shorting permanently. While diodes are cheaper than a good MOSFET transistor, unless you're good with a microscope the scanner still has to go back for repair.

2) If the scanner design is just the least bit skimpy, the front end will go at a signal level just under one that will destroy the diodes (assuming there are protection diodes in an el cheapo scanner) and it's most sensitive on the band it's tuned to.

Bottom line is, for best protection, turn the scanner off and disconnect the antenna in a high-RF environment. Wear a belt and suspenders. Wear rubbers over your boots, in case a boot springs a leak.

Or not.

and dont pull the mask off the old lone ranger and dont mess around with Jim!...
Thanks for the info... It hepled

 

[Buckskinner33]

No, but I am monitoring the 150 and 450-460 bands on my scanner while talking on my 100 watt Motos on the 150 and 450-460 bands, as well as on the 2m and 70cm bands on my ham rigs.

I can't say about the construction of the Pro-95, but as a general rule, handhelds are more susceptable to overload and desense, simply because there isn't as much room in the smaller case for better filters. As for actually destroying the scanner, I haven't seen that happen, although I have heard anecdotal evidence.

Mark S.

Thanks for the info... Just for the record...Its usually not tapped into any external antenna, I just use the 800 MHz duck.