[hpsdr] Mercury Spurious Emissions

[Joe Martin K5SO]

Jeremy,

Be careful not to confuse signals that you may "see" by using a VHF  
receiver to look for signals coming out of Mercury with actual RF  
radiating from the Mercury connector.  What you may be proving is that  
the VHF receiver you're using as a test receiver is a poor performer  
in eliminating/reducing any of a variety of image frequencies, not  
that Mercury itself has dramatic spurious emission problems.

True, the Mercury board is at least providing a 122.88 MHz source for  
the "test" receiver to mix with its local oscillators to produce what  
appears to be emissions coming from Mercury but those "signals" you  
see are probably not actually radiating from Mercury itself, instead  
they may actually be generated within your test receiver by mixing  
with the 122.88MHz and multiples thereof that are being radiated from  
Mercury.

73,  Joe K5SO

On Sep 10, 2011, at 9:45 AM, Jeremy McDermond wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> On Sep 10, 2011, at 12:00 AM, Helmut Oeller wrote:
>
>> Hi Jeremy,
>>
>> It's possible that you receive the 122,88 Mc sampling clock due to  
>> a bad
>> image rejection of the FM rig, if its if is around 10.7 Mc. In  
>> particular
>> hand-held FM rigs have bad selection in the frontend.
>
> I have checked on the IF frequency of the TH-D7A, and the first IF  
> is supposed to be at 38.85MHz on 2m.
>
> From Steve's dataset, it seems like it's harmonics of 3.072 that are  
> being radiated somehow.
>
> I'm seeing signals at:
>
> Signal -- Harmonic (predicted frequency)
> ------------------------------
> 138.245 -- 45th (138.240)
> Not Hrd -- 46th (141.312)
> 144.385 -- 47th (144.384)
> 147.455 -- 48th (147.456)
> 150.525 -- 49th (150.528)
> Not Hrd -- 50th (153.600)
> 156.675 -- 51st (156.672)
> 159.745 -- 52nd (159.744)
> 162.815 -- 53rd (162.816)
> Not Hrd -- 54th (165.888)
> 168.960 -- 55th (168.960)
> 172.030 -- 56th (172.032)
>
> 402.435 -- 131st (402.432)
> 405.505 -- 132nd (405.504)
> 408.575 -- 133rd (408.576)
> Not Hrd -- 134th (411.648)
> 414.720 -- 135th (414.720)
> 417.795 -- 136th (417.792)
> 420.865 -- 137th (420.864)
> Not Hrd -- 138th (423.936)
> 427.005 -- 139th (427.008)
> 430.080 -- 140th (430.080)
> 433.150 -- 141st (433.152)
> 436.225 -- 142nd (436.224) -- Weak
> 439.295 -- 143rd (439.296)
> 442.365 -- 144th (442.368)
> 445.440 -- 145th (445.440)
> Not Hrd -- 146th (448.512)
> 451.585 -- 147th (451.584)
> 455.655 -- 148th (454.656)
> 457.725 -- 149th (457.728)
> 460.800 -- 150th (460.800) -- Weak
> 463.870 -- 151st (463.872)
> 466.945 -- 152nd (466.944)
> 470.015 -- 153rd (470.016)
> Not Hrd -- 154th (473.088)
> 476.160 -- 155th (476.160)
> 479.235 -- 156th (479.232)
>
> So, it appears as though the theory of 3.072MHz harmonics is  
> correct, although it appears as though every 4th harmonic is being  
> suppressed by something.
>
>> 73 Helmut, DC6NY
>
> --
> Jeremy McDermond (NH6Z)
> Xenotropic Systems
> mcdermj at xenotropic.com
>
>
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at openhpsdr.org
> Subscription help: http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
> HPSDR web page: http://openhpsdr.org
> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/


 1315670676.0