[CQ-Contest] LP SO2R with no filters?

Steve London n2icarrl at gmail.com
Wed Jun 17 18:27:23 EDT 2015

If they were using 1975-vintage radios, with vacuum tube front ends, I'm 
not surprised there was no damage. And if there was damage, I wonder if 
the typical, non-contester, Field Day operator would even notice !

Operating with a "general purpose" radio club, how many times have we 
walked up to a Field Day operator, on what should be a wide-open band, 
only to discover he/she as made no QSO's in the last hour ? We snoop 
around, and discover obvious issue(s).

Steve, N2IC

On 06/17/2015 06:49 AM, Joe wrote:
> I'm curious,
> This conversation has been interesting for sure. But I wonder if the
> risk of damage has or is being exaggerated some. Reason thinking this is
> for one thing. What is gonna happen in a little over a week. Field Day.
> Field Day, pushes the damage potential to the extreme far more than SO2R
> could ever be. And in many instances filters are not even an option for
> protection. As in the case of a say 40 meter phone station, CW station,
> and ex Novice Station ( Now the GOTA Station ) all on 40 meters at the
> same time.
> Yet I have been doing Field Day since 1975, from simple 1A efforts to
> 2A   or 5A and even up to once a 12A group. Yet I have not in my mind
> ever known of any damage that has ever happened to any of the rigs. Even
> one group one year was a 3 A Operation and all they had were multi band
> verticals for each station and they were all mounted on the same barb
> wire fence than was their ground system. and the 3 antennas were at the
> most maybe 100 feet apart MAX. Granted in this setup they were not able
> to operate all 3 on the same band, the overload desence was terrible.
> sounded like a big vacuum cleaner on the band sucking up all the
> signals, but no damage happened.
> Hmmmm?
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 6/16/2015 5:14 PM, Jeff AC0C wrote:
>> The amount of work a guy may want to put into checking out the setup
>> for isolation is in direct proportion to the cost of getting a
>> potentially expensive RX repaired.  My view is that until you have
>> TESTED to BE SURE the isolation exists, you have to assume it's going
>> to fry gear.
>> And don't let the thought that "I'm only running 100W" be of any
>> consideration.  That's +50 dBm and you want to be very much under +20
>> dBm to avoid damage - and less than that in some cases.  I think W2VJN
>> recommends 0 dBm as the damage threshold target.  That means you need
>> 30-50 dB of isolation, on every band and directional combo - something
>> which takes time to check out.   The isolation is easy to achieve with
>> natural coupling loss and a stub.
>> You really will probably not be happy if you just try it, trusting
>> luck alone, only to find out luck ends up against you.
>> 73/jeff/ac0c
>> www.ac0c.com
>> alpha-charlie-zero-charlie
>> -----Original Message----- From: Jeff Stai
>> Sent: Tuesday, June 16, 2015 12:31 PM
>> To: Mike Smith VE9AA
>> Cc: cq-contest
>> Subject: Re: [CQ-Contest] LP SO2R with no filters?
>> On Mon, Jun 15, 2015 at 2:53 PM, Mike Smith VE9AA <ve9aa at nbnet.nb.ca>
>> wrote:
>>> Has anyone ever done SO2R with no bandpass filters?
>> Buy the W2VJN book from Inrad. It will explain everything:
>> http://www.qth.com/inrad/book.htm
>> But in a nutshell, just try it. It sounds like you have both
>> horizontal and
>> vertical antennas, which will give you 20dB of separation at the outset.
>> That could very well be enough for your conditions. If you need more,
>> stub
>> filters can be very effective for the cost of some scrap coax.
>> 73 jeff wk6i
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