Receiving 4th Harmonic of AM Station

[Rick Stealey]

So now we know it wasn't caused by overload.  But since I went to the trouble of hauling my signal generator up to the shack and connecting it to my K3 I figured you guys might like to know how your K3 will stand up to a big signal on the broadcast band.  Let's not be so quick to assume this fantastic receiver can be overloaded to the point where it generates 20 over 9 signals on 160 and 80 meters !!!!!!!

The 8640B is connected to the K3 through a coupler, and the antenna is connected to the other port.  The generator is tuned to 940 KHz and the K3 is tuned to 1880 and 3760.
The generator is cranked up till the K3 hears a signal at about S5 on 1880, a little over my local static level.  The generator is putting out -40 dbm.  S5 is about a -100 dbm signal.  
Most likely the S5 signal is the 2nd harmonic of the signal generator, 60 db down, not caused by the K3, because guess why?  Because putting the attenuator on doesn't kill the signal like it would if it was internally generated.  Your K3 isn't going to be bothered by killer AM broadcast band signals, at least not to the point where it generates 20 over 9 spurs, fear not !!

Just for kicks (I've always wanted to do this) I tuned in some EU stations around 7008.
Then set the generator to -20 dbm.  Now let me tell you , -20 dbm is one, friggin, HUGE signal. And tuned it down the band until its effect was noticible on the weak signals.  Want to guess how close I could get?  7008.3 !!   300 cycles away from weak Europeans, with a 60 db over 9 interfering signal!!!!

Rick  K2XT
     
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[Brett Howard]

Very nice!!  Fun test... You're nuts!  But hey so am I.  I take it you
have the 250Hz 8-pole filter in your radio in order for that to happen?

~Brett (N7MG)

On Fri, 2010-07-23 at 23:34 +0000, Rick Stealey wrote:

>
> So now we know it wasn't caused by overload.  But since I went to the trouble of hauling my signal generator up to the shack and connecting it to my K3 I figured you guys might like to know how your K3 will stand up to a big signal on the broadcast band.  Let's not be so quick to assume this fantastic receiver can be overloaded to the point where it generates 20 over 9 signals on 160 and 80 meters !!!!!!!
>
> The 8640B is connected to the K3 through a coupler, and the antenna is connected to the other port.  The generator is tuned to 940 KHz and the K3 is tuned to 1880 and 3760.
> The generator is cranked up till the K3 hears a signal at about S5 on 1880, a little over my local static level.  The generator is putting out -40 dbm.  S5 is about a -100 dbm signal.  
> Most likely the S5 signal is the 2nd harmonic of the signal generator, 60 db down, not caused by the K3, because guess why?  Because putting the attenuator on doesn't kill the signal like it would if it was internally generated.  Your K3 isn't going to be bothered by killer AM broadcast band signals, at least not to the point where it generates 20 over 9 spurs, fear not !!
>
> Just for kicks (I've always wanted to do this) I tuned in some EU stations around 7008.
> Then set the generator to -20 dbm.  Now let me tell you , -20 dbm is one, friggin, HUGE signal. And tuned it down the band until its effect was noticible on the weak signals.  Want to guess how close I could get?  7008.3 !!   300 cycles away from weak Europeans, with a 60 db over 9 interfering signal!!!!
>
> Rick  K2XT
>      
> _________________________________________________________________
> Hotmail is redefining busy with tools for the New Busy. Get more from your inbox.
> http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_2
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[Geoffrey Mackenzie-Kennedy]

You should try living with the 40m BC stations heard here and working SSB DX
among them, at peak time their carrier levels can reach a measured +5 to +10
dbm off a 70 ft high dipole. They were supposed to vacate 7100 -71200, but
not all have got the message it seems.

73,

Geoff
GM4ESD


On Saturday, July 24, 2010 at 1:04 AM, Brett Howard wrote:

> Very nice!!  Fun test... You're nuts!  But hey so am I.  I take it you
> have the 250Hz 8-pole filter in your radio in order for that to happen?
>
> ~Brett (N7MG)


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