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Receiver Damage from another Close Station?

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w0ih

Receiver Damage from another Close Station?

My next door neighbor is a ham and recently upgraded to a Icom 7700, 200 watt.

The antennas for my K3 are pretty close to his. I have a set of dipoles (160, 75, 60 that share a common feedline) that are about 30 feet off one leg from the neighbor's HyTower (75 thru 10 full size vertical). I have a TH11DX up at 50 feet (boom is loaded for 40 meters also, separate feedline) and he has a TH5DX at very close to the same level, directly east of my tower, about 100 feet away.

I have a Heathkit SB 220 amp (2 kw input?). Neighbor runs barefoot for now.

So, my question is, do I need to be concerned about damage to either rig? I'm assuming that we can't operate the same bands at the same time. Our operating schedules seem to be very different for now. But I'm wondering if there could be input damage from one operating on any band, even if the rig is off.

I was wondering if the K3 input is grounded through a relay when turned off, and similarly on the 7700.

Any thoughts?

Mike

w0mu

Re: Receiver Damage from another Close Station?

Yes you should be concerned. I would think about bandpass filtering and
probably disconnecting the K3 when not on the air. I was looking at the
mods for the K3 and noticed one that addressed this issue.

Are we talking city lot or 20 acre parcels?

W0MU

On 3/2/2011 6:38 PM, w0ih wrote:

> My next door neighbor is a ham and recently upgraded to a Icom 7700, 200
> watt.
>
> The antennas for my K3 are pretty close to his. I have a set of dipoles
> (160, 75, 60 that share a common feedline) that are about 30 feet off one
> leg from the neighbor's HyTower (75 thru 10 full size vertical). I have a
> TH11DX up at 50 feet (boom is loaded for 40 meters also, separate feedline)
> and he has a TH5DX at very close to the same level, directly east of my
> tower, about 100 feet away.
>
> I have a Heathkit SB 220 amp (2 kw input?). Neighbor runs barefoot for now.
>
> So, my question is, do I need to be concerned about damage to either rig?
> I'm assuming that we can't operate the same bands at the same time. Our
> operating schedules seem to be very different for now. But I'm wondering if
> there could be input damage from one operating on any band, even if the rig
> is off.
>
> I was wondering if the K3 input is grounded through a relay when turned off,
> and similarly on the 7700.
>
> Any thoughts?
>
> Mike
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Receiver-Damage-from-another-Close-Station-tp6083308p6083308.html
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N7US

Re: Receiver Damage from another Close Station?

Before I got my K3 I had a ham move in 1000' from my antenna, and I wasn't
pleased. In my previous location in AZ, I was 1700' from a ham too.

In both cases, I used an ICE front-end saver, which is cheap insurance. See
http://www.iceradioproducts.com/reconly.html#rflimiter .

I used a Model 196, but I see they also have a model that includes a
lightning arrestor / static drain, and another pair for 30-500 MHz.

I'd like to hear from someone more technically qualified than I am (that
means almost anyone) about the adequacy of the ICE units.

My last neighbor was in a rental house. He moved out after a year, and I
breathed a sigh of relief.

Jim N7US

-----Original Message-----

Yes you should be concerned. I would think about bandpass filtering and
probably disconnecting the K3 when not on the air. I was looking at the
mods for the K3 and noticed one that addressed this issue.

Are we talking city lot or 20 acre parcels?

W0MU

On 3/2/2011 6:38 PM, w0ih wrote:
> My next door neighbor is a ham and recently upgraded to a Icom 7700, 200
> watt.
>
> The antennas for my K3 are pretty close to his. I have a set of dipoles
> (160, 75, 60 that share a common feedline) that are about 30 feet off one
> leg from the neighbor's HyTower (75 thru 10 full size vertical). I have a
> TH11DX up at 50 feet (boom is loaded for 40 meters also, separate
feedline)
> and he has a TH5DX at very close to the same level, directly east of my
> tower, about 100 feet away.
>
> I have a Heathkit SB 220 amp (2 kw input?). Neighbor runs barefoot for
now.
>
> So, my question is, do I need to be concerned about damage to either rig?
> I'm assuming that we can't operate the same bands at the same time. Our
> operating schedules seem to be very different for now. But I'm wondering
if
> there could be input damage from one operating on any band, even if the
rig
> is off.
>
> I was wondering if the K3 input is grounded through a relay when turned
off,
> and similarly on the 7700.
>
> Any thoughts?
>
> Mike

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John Ragle

Re: Receiver Damage from another Close Station?

Second to that concern. I burned up the 2 meter GaAsFET preamp/relay in
my TE Systems amp while running my 6 meter amp to its Yagi on the same
Christmas tree.

John Ragle -- W1ZI

=====

On 3/2/2011 9:29 PM, Jim McDonald wrote:

> Before I got my K3 I had a ham move in 1000' from my antenna, and I wasn't
> pleased. In my previous location in AZ, I was 1700' from a ham too.
>
> In both cases, I used an ICE front-end saver, which is cheap insurance. See
> http://www.iceradioproducts.com/reconly.html#rflimiter .
>
> I used a Model 196, but I see they also have a model that includes a
> lightning arrestor / static drain, and another pair for 30-500 MHz.
>
> I'd like to hear from someone more technically qualified than I am (that
> means almost anyone) about the adequacy of the ICE units.
>
> My last neighbor was in a rental house. He moved out after a year, and I
> breathed a sigh of relief.
>
> Jim N7US
>
>
>
> -----Original Message-----
>
>
> Yes you should be concerned. I would think about bandpass filtering and
> probably disconnecting the K3 when not on the air. I was looking at the
> mods for the K3 and noticed one that addressed this issue.
>
> Are we talking city lot or 20 acre parcels?
>
> W0MU
>
> On 3/2/2011 6:38 PM, w0ih wrote:
>> My next door neighbor is a ham and recently upgraded to a Icom 7700, 200
>> watt.
>>
>> The antennas for my K3 are pretty close to his. I have a set of dipoles
>> (160, 75, 60 that share a common feedline) that are about 30 feet off one
>> leg from the neighbor's HyTower (75 thru 10 full size vertical). I have a
>> TH11DX up at 50 feet (boom is loaded for 40 meters also, separate
> feedline)
>> and he has a TH5DX at very close to the same level, directly east of my
>> tower, about 100 feet away.
>>
>> I have a Heathkit SB 220 amp (2 kw input?). Neighbor runs barefoot for
> now.
>> So, my question is, do I need to be concerned about damage to either rig?
>> I'm assuming that we can't operate the same bands at the same time. Our
>> operating schedules seem to be very different for now. But I'm wondering
> if
>> there could be input damage from one operating on any band, even if the
> rig
>> is off.
>>
>> I was wondering if the K3 input is grounded through a relay when turned
> off,
>> and similarly on the 7700.
>>
>> Any thoughts?
>>
>> Mike
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>
>

Jim Brown-10

Re: Receiver Damage from another Close Station?

In reply to this post by w0ih

On 3/2/2011 5:38 PM, w0ih wrote:
> My next door neighbor is a ham and recently upgraded to a Icom 7700, 200
> watt.

This is the sort of operating conditions that we typically set up for
California QSO Party county expeditions, and that also occur at some
contesting stations (like PJ2T, PJ4A, N6RO, etc.). The CQP group that I
go with uses K3s driving 500w amps, wire dipoles, and tri-banders on
tower trailers roughly 130 ft apart. Stations like this will typically
use very good bandpass filters between the rig and the power amp
(usually W3NQN filters) and also stubs following the power amp. Antennas
are usually carefully arranged to minimize the coupling between them,
and most contests, stations are on different bands. In CQP though, we
often had a CW and SSB station on the same band. Filters don't help with
that -- it takes separation of antennas.

At CQP, we had one incident of actual damage to a K3. It happened
because both CW and SSB were on 40M at the same time, using dipoles that
were end to end with only a few feet between them. That's dumb, but we
did it. :) We had no problems with both stations being on 15M or on
20M, and the year after blowing up the front end with the 40M dipoles
end to end, we moved the dipoles much further apart.

Also, at CQP, our tri-banders were carefully arrayed so that they were
essentially parallel to each other when pointed where we intended to
operate them. That greatly reduces the coupling between them as
compared to pointing them at each other -- I'd guess a difference of
roughly 30-50dB (30-300 times less voltage by having each in the null of
the other's pattern, as opposed to 6dB of gain from each).

One of the best resources on this is W2VJN's book on Managing
Interstation Interference. Buy it from Inrad (the folks who sell the
crystal filters) for about $25. George talks about how to calculate and
how to measure the coupling between antennas, how much RF voltage it
takes to cause damage, how to reduce the coupling with filters and
stubs. Very solid engineering, very practical, written at a very
understandable level. George is a contributor to the ARRL Handbook.

73, Jim K9YC
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Pete Smith N4ZR

Re: Receiver Damage from another Close Station?

In reply to this post by w0ih

When I set my station up for single-tower SO2R, I was concerned about
what would happen when I split my tribander stack, and when I operated
on 40 and 15. I had bandpass filters but figured that at some time I
would make an expensive mistake, so I cobbled up a receiver protector.
Details and a schematic are at
<http://pvrc.org/~n4zr/Articles/Simple%20Protection%20for%20the%20Fledgling%20SO2R%20Station.pdf>.
Should cost you only a few bucks.

73, Pete N4ZR

The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com,
spots at telnet.reversebeacon.net, port 7000

On 3/2/2011 8:38 PM, w0ih wrote:

kcflyers

Re: Receiver Damage from another Close Station?

Pete - your link doesn't work. John.

Shel Radin KF0UR

Re: Receiver Damage from another Close Station?

In regards to the link not working, just get rid of the < and > at the beginning and end of the URL and it should work OK. It did for me.

w0ih

Re: Receiver Damage from another Close Station?

I may have to build a circuit to add some protection.

But I'm not sure where I add it in. I want it in the receive line, but not in the transmit line. Is there somewhere in the K3 that I can tap off to limit the input signal?

Mike