VHF weak signal meeting at Visalia DX convention

[n7stu at valleynet.com]

I will be attending the Visalia DX convention again this year and was
thinking it would be nice to meet other weak signal types who are there
also.  Last year I was surprised to run into AA7A.  

If you are going to Visalia and are interested in an informal get
together/BS session drop me a note and I will try to arrange a
time/location.  I will only be there Saturday and thus don't have a room,
but if anyone is interested in donating their room for a couple of hours
that would be perfect.

If you don't know about the Visalia DX convention it will be held on April
19,20,21 at the Holiday Inn in Visalia, CA.

73, Robert N7STU/YB2ARO, DM07aa/OI52ee

n7stu at valleynet.com
http://www.valleynet.com/~n7stu (WSWSS mirror & N7STU/YB2ARO homepages)


>From Brian K. Short" <ke7gh at primenet.com  Sat Apr  6 15:30:31 1996
From: Brian K. Short" <ke7gh at primenet.com (Brian K. Short)
Date: Sat, 6 Apr 1996 15:30:31 +-100
Subject: Amplifier Question
Message-ID: <01BB23CE.18A19B60 at ip087.phx.primenet.com>

I am looking for an amplifier to handle 1kw to 1.5kw key down RTTY.
Please don't flame me over advertising here, I just want to know 
where to look?  I have tried VHF packet, USENET, packet cluster, etc.
Where does one find a good used amp for RTTY/contesting for sale?
I had an offer for a single 3-500Z amp, but clearly this is not it!

Where does one find used Henry, Alpha, etc amps for sale.  I am a
bit isolated in Phoenix, but I would drive to Southern California
for the right amp if it is that heavy.

How do I find it?

BTW I have all the literature from Alpha, Henry, Command, QRO...
I am very serious, but would prefer a peice of used equipment
even homebrew at this time...for various reasons...

73 de Brian


>From John Sweeney <jsweeney at pop.wwa.com>  Sat Apr  6 15:40:39 1996
From: John Sweeney <jsweeney at pop.wwa.com> (John Sweeney)
Date: Sat, 06 Apr 1996 09:40:39 -0600
Subject: antenna heights
References: <m0u5Y2N-000MIyC at Mufasa.AGN.NET>
Message-ID: <31669077.3C06 at pop.wwa.com>

Ken,

I'm not sure you will see much of a difference between 65 and 80 feet on 20m,
unless you are in a low spot, but I can guarantee you will notice the difference
between a rotatable dipole and a 2 el (even shorty) yagi on 40m.  Both my friend,
K9NB and myself have had KLM dipoles at 80 ft and switched to the HyGain Discoverer
2 el.  BIG difference.  We estimate about 5-6 dB.  At weak signal levels, another
5-6 dB opens up a whole new additional layer of DX stations.

73, John K9EL

Kenneth Dul wrote:
> 
> Question for the antenna gurus out there:
> 
> I'm wondering if there would be a difference, especially on 20, between
> having a TH-7/KT-34XA at 65 feet vs. 80 feet. I'm in Michigan, fairly
> flat land. Choice of towers is what is driving this question.
> 
> Also, at 70 feet would I see any difference between a rotable dipole
> and a 2 element shorty forty like the Cushcraft 402CD on 40 meters?
> 
> This is all for DX'ing purposes. I'm not a BIG GUN contester, but a
> little pistol. And mainly interested in keeping the country total at the
> top and working new band countries as they come along on cw.
> 
> Any preferences for either a TH-7 or KT-34XA?? :-)  (yup, I know a loaded ?)
> 
> tnx es 73's
> Ken K8ZR

>From Paul Erickson <paul1 at wizard.ucs.sfu.ca>  Sat Apr  6 15:48:32 1996
From: Paul Erickson <paul1 at wizard.ucs.sfu.ca> (Paul Erickson)
Date: Sat, 6 Apr 96 7:48:32 PST
Subject: Contest Exchange
Message-ID: <9604061548.AA18948 at wizard.ucs.sfu.ca>

Hi Trey,

Your comments are no doubt valid for the vast majority of contesters, but
some of us find the power designation really helpful. Running in the
qrp catagory with fixed antennas, knowing   the power a station is running
really helps in determining if the station is one to go for, or to pass on.

If I hear a station that is actually 57 signing "kw" then I know to pass and
wait til it is 59 or better. This saves futile effort on my part and qrm
for others. If the station is 57 and signs 100, I know he/she is worth going
for.

Given that there are so few of us , I don't expect this to have any effect
in terms of changing anything or keeping anything the same, but just thought
you ought to know that for some the power is more informative than the zone.

cheers, Paul
ve7cqk
email: paul1 at wizard.ucs.sfu.ca

> 
> I think the contest that has taken the most abuse through the years
> about it's exchange in the ARRL DX Contest.  If people still have
> their minds set to change the exchange in this contest, I would
> suggest a meaningless signal report (599 would be good) plus ITU zone.
> Leave things the same for the stateside guys, 599 + state.  Why?
> Because from an operational perspective the ITU zone is much more
> informative than power level, although that information is kinda fun
> too (vive la difference, remember?).
> 
> --Trey, WN4KKN/6
> 


>From Del Seay <seay at alaska.net>  Sun Apr  7 00:52:03 1996
From: Del Seay <seay at alaska.net> (Del Seay)
Date: Sat, 06 Apr 1996 16:52:03 -0800
Subject: antenna heights
References: <m0u5Y2N-000MIyC at Mufasa.AGN.NET>
Message-ID: <316711B3.667E at alaska.net>

Kenneth Dul wrote:
> 
> Question for the antenna gurus out there:
> 
> I'm wondering if there would be a difference, especially on 20, between
> having a TH-7/KT-34XA at 65 feet vs. 80 feet. I'm in Michigan, fairly
> flat land. Choice of towers is what is driving this question.
> 
> Also, at 70 feet would I see any difference between a rotable dipole
> and a 2 element shorty forty like the Cushcraft 402CD on 40 meters?
> 
> This is all for DX'ing purposes. I'm not a BIG GUN contester, but a
> little pistol. And mainly interested in keeping the country total at the
> top and working new band countries as they come along on cw.
> 
> Any preferences for either a TH-7 or KT-34XA?? :-)  (yup, I know a loaded ?)
> 
> tnx es 73's
> Ken K8ZR


You have to know where your reflective ground is to properly answer
that question. And, I have never been able to do that!
What I have found, as a matter of experience, is to make my height
jumps in 1/4 wave steps at the lowest qrg. I find that going from 
35'to 50'seems to make very little difference.(Assuming no physical
obstacles to clear such as trees, bldgs etc.) But, go from 50 feet
to 70 feet and you seem to have a whole new world. The same going to
100' as opposed to 85'. Of course I'm talking about low angle stuff
such as to EU and AFR.
Have fun.  Del, KL7HF

to make no

>From Ward Silver <hwardsil at wolfenet.com>  Sat Apr  6 17:14:51 1996
From: Ward Silver <hwardsil at wolfenet.com> (Ward Silver)
Date: Sat, 6 Apr 1996 09:14:51 -0800 (PST)
Subject: QDC
Message-ID: <Pine.OSF.3.91.960406091051.22224J-100000 at gonzo.wolfenet.com>


Sending your call with every QSO also serves as a "sync pulse" to keep 
everyone, well, in sync.  "TU" or "R" is too short to be heard by 
everyone, particularly if you're going fast.  The slower in the pile 
won't hear the short turnaround and will become confused, call at an 
inappropriate time, and bollix the whole thing in short order.  Your 
call is long enough to just about guarantee that everyone will hear it 
and act accordingly. 

Of course, if your call is WN4KKN/HC8, you might want to re-think this 
option ;-)

73, Ward N0AX

>From John Brosnahan <broz at csn.net>  Sat Apr  6 06:20:21 1996
From: John Brosnahan <broz at csn.net> (John Brosnahan)
Date: Fri, 5 Apr 1996 23:20:21 -0700
Subject: 4-1000 Info Please?
Message-ID: <199604060620.XAA27955 at lynx.csn.net>


>>Just grounding both the grid and screen in the 4-400, 4-1000
>>series tubes resulted in the grid hogging the current and limiting
>>the tubes capabilities.   A technique to provide better division 
>>of current between the grid and screen in grounded grid is to
>>tap the grid connection down on the filament choke.  This results
>>in some RF being applied to the grid as well as the cathode and
>>the tube will have a better balance between grid and screen
>
>That's a bad scheme to use in the general case. The grid is no longer
>grounded, and this adds positive feedback to the stage. It decreases
>stability and increases IMD. The grid ALL should be grounded for RF in a GG
>amp. The correct way to "balance" the currents without adding unwanted
>feedback is by the addition of regulated dc supply voltage to the heavily
>bypassed screen and grid elements.
>   
>73 Tom  W8JI

I believe that the technique of tapping the grid up on the cathode RF
choke provides some negative feedback which is why the stage
requires more drive when operated this way.  The stability issue is
pretty much taken care of by the well grounded screen.  Negative
feedback typically improves IMD but the IMD varies enough over
the entire operating range of the tube that making generalizations
based on making measurements near a cusp on the IMD curve
may lead to the wrong conclusions about how great the improvement
might be.

Operating a tube such as the 3CX300A in super-cathode-driven 
service compared to grid driven service can improve the 3rd order
IMD from -27 dB to -46 dB and the 5th order from -36 dB to -49 dB.  
Quite an improvment.  I don't have data at hand to show the 
improvement for tubes such as the 4-400 and 4-1000 but it
should be comparable.  Of course the improvement of super-cathode-
driven service over regular cathode driven service won't be as great.

Adding grid and screen supplies increases the complexity and
will move the operating conditions from the Class B region to the 
Class AB1 region.  Power gain is essentially established by the screen
voltage and static (resting) plate current is set by the grid bias.
So a simple variable screen supply can be added if a variable
gain amplifier stage is desired.

The super-cathode-driven technique is probably a more important
option for the 4-400 with its more fragile grid and screen than for
the more rugged 4-1000.  Tapping down about 1/5 of the way from
cathode end of the cathode RF choke should be about right.  For
a tetrode there should be no stability problems but I don't think I
would try this with a triode.

Info on Semi- and Super-Catode-Driven Amplifiers is available from 
QST p 34  July 1967
Ham Radio p 73 Nov 86
Ham Radio p 43 Feb 87 with a minor correction in HR p 50 Apr 87

73  John  W0UN



John Brosnahan  
La Salle Research Corp      24115 WCR 40     La Salle, CO 80645  USA
voice 970-284-6602            fax 970-284-0979           email broz at csn.net