[ICOM] 7600 and Dual Watch... "it's a mix"

Fri Aug 21 14:43:40 EDT 2009

Gordon,
    I guess all your antennas are on the same tower so you can run then 
as a stack in a single direction, hence the equal lengths of coax. I 
typically feed antennas on different towers, usually pointed in 
different directions for HF or 6m. sometimes I have to play with the 
coax lengths to get less than 1.7:1 with all combinations.
    Phil N0KE

J. Gordon Beattie, Jr., W2TTT wrote:
> Phl,
> I have access to one, but that doesn't protect the second rig...I guess your
> suggestion is that I consolidate to one rig and phase the antennas through
> the Stackmatch with equal coax lengths et al.  I certainly could do that,
> but I would need to think about what happens when the patterns interact as
> the antennas are on separate rotators and sometimes point across each
> other's paths.
> Hmmm...
> :-)
> Nice problem to consider...
> :-)
> Thanks & 73,
> Gordon Beattie, W2TTT
> 201.314.6964
>  
>
> -----Original Message-----
> From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
> Behalf Of Phil Krichbaum
> Sent: Friday, August 21, 2009 6:48 AM
> To: ICOM Reflector
> Subject: Re: [ICOM] 7600 and Dual Watch... "it's a mix"
>
> Gordon,
>     A simpler solution  is to use one of the WX0B StackMatches that 
> allows one to TX/RX on one, two or three antennas at once. For TX the 
> SWR on no one antenna can exceed about 1.7:1. These cover from 160 thru 
> 6m. I live in CO and in a 6m contest it is often possible to have the 
> band open in  two or three or even more directions at once. If you are 
> running 1500w, you can CQ with 500w in three directions at once which is 
> quite effective. It is also handy for HF contesting and even with QRP 
> I'll split the power between multiple antennas. It is handy for S&P to 
> listen in multiple directions and quite easy to switch all the juice to 
> a single antenna to make the QSO. From TI5N I would CQ with 2.5w to 
> Europe and 2.5 to the US and would run stations in both at the same 
> time. Jay (WX0B) could not believe I was able to do it at that power level!
>     Be carefull with the II and III as the front ends are very poorly 
> protected from nearby RF or ESD sources. Been there done that 5 times 
> with my III at about $250 per repair!
>     Phil N0KE
>
> J. Gordon Beattie, Jr., W2TTT wrote:
>   
>> Adam et al,
>> I guess you could use a second receiver with an IC-756PROIII as well using
>> the splitter et al?  
>>
>> I've been thinking a bit differently about this dual receive situation
>> because of the performance issues that sometimes come up, but more
>> importantly because of the operational requirements that I have.  It might
>> be cool to set up my PRO3 and PRO2 in a SO2V/SO2R configuration using two
>> separate 6M antennas and just protect whichever transceiver is idle when I
>> transmit with the other one.  The same strategy could be done on 20M, 40M,
>> etc.  I am blessed with separately rotatable antennas on different towers
>> which allows me to look west and south or northeast toward Europe while
>>     
> also
>   
>> looking west or south as needed.  
>>
>> I am thinking about using some small BNC Dow-Key relays and small dummy
>> loads all triggered by reed relays from the rigs and the PTT lines, as I
>> only use the exciters here with no amps.
>> Thoughts?
>>
>> Thanks & 73,
>> Gordon Beattie, W2TTT
>> 201.314.6964
>>  
>> -----Original Message-----
>> From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net]
>>     
> On
>   
>> Behalf Of Adam Farson
>> Sent: Thursday, August 20, 2009 6:25 PM
>> To: 'ICOM Reflector'
>> Subject: Re: [ICOM] 7600 and Dual Watch... "it's a mix"
>>
>> Hi Dick,
>>
>> Dual Watch exacts two penalties in terms of RF performance:
>>
>> 1. When DW is activated, the noise-band (idle-channel noise) at the Sub
>> frequency is added to that at the Main frequency. This raises the system
>> noise floor by 3 dB.
>>
>> 2. There is an RF make-up amplifier ahead of each first mixer, and an IF
>> make-up amplifier at the IF output of each mixer. These amplifiers make up
>> the insertion loss of the splitter and combiner, respectively. The
>>     
> presence
>   
>> of these amplifiers in the RF and 1st IF signal paths will degrade
>>     
> IMD-free
>   
>> dynamic range.
>>
>> http://www.ab4oj.com/icom/dw.html 
>>
>> There are other factors in the superior receiver performance of the 7700
>>     
> vs.
>   
>> 7600. The 7700 first mixer is a passive DMOS switch vs. a more
>>     
> conventional
>   
>> quad-JFET mixer in the 7600. The 770 mixer will thus have superior
>> strong-signal handling. In addition, the 7700 receiver has dedicated,
>> relay-switched RF bandpass filters and a tracking preselector (Digi-Del),
>> vs. diode-switched shared filters and no preselector in the 7600. (Relay
>> switching eliminates another IMD contributor.)
>>
>> It is not too difficult to multicouple a second receiver to the 7700.
>>
>> http://www.ab4oj.com/icom/ic7700/2rx.html
>>
>> Cheers for now, 73,
>> Adam VA7OJ/AB4OJ
>>
>>
>> -----Original Message-----
>> From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net]
>>     
> On
>   
>> Behalf Of Dick Flanagan
>> Sent: 20-Aug-09 11:05
>> To: ICOM Reflector
>> Subject: Re: [ICOM] 7600 and Dual Watch... "it's a mix"
>>
>> Having Dual Watch compromises the performance of the receiver.  You can
>>     
> have
>   
>> good performance with Dual Watch or better performance without it.  The
>>     
> 7700
>   
>> chose to go the route of maximum performance.
>>
>> I would be curious to know if without Dual Watch the 7600 receive
>> performance could have equaled that of the 7700.  If it could, it might
>>     
> have
>   
>> impacted sales of the 7700.
>>
>> Dick
>> --
>> Dick Flanagan K7VC
>> dick at k7vc.com
>>
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