Output Spike on Icom-706

[AA6KX at aol.com]

In preparing for an upcoming CONTEST expedition for WPX, I recently set out
to test my new Icom 706 with my Alpha 87A.  I know this is a bizarre
combination, but I'm looking at the 706 as a backup rig.  (Incidentally, my
apologies to all who were in the Sunday morning 40/20m pileup on KH6CC during
ARRL-CW and couldn't understand why I didn't answer them and just kept on
CQing.  It turns out the receive oscillator on my main rig had suddenly taken
a sideways step. We finally found the pile-up by using a second rig and I
finished out the contest with a whole lot of RIT dialed in!)

Anyway, when I try to drive the 87A with the 706 I see some very unexpected
behavior.  No matter how low I set the drive power on the 706, the very first
dit I send causes the power output lights on the Alpha to flash full scale.
 Succeeding dits which are closely spaced will give the expected power
reading based on the amount of drive supplied.  In SSB, a similar situation
holds.  I can pull down PTT so that all the T/R switching is complete but
then the first bit of audio supplied causes a momentary full-scale reading on
the 87A's power meter.  After that momentary flash, the reading is expectable
in the same way as it is in CW.  

In the course of making these tests, I noticed one other interesting piece of
data.  If I wait a half second or so after the first dit before sending a
second dit, then the second dit will cause a power reading which is still
excessive but less than full scale and reduced by an amount proportional to
the time elapsed since the first dit.  To give an example of the pattern, a 1
second delay might show 1KW out, a 2 second delay 800w, and so forth.

I first contacted Icom Customer Service about this and they had no
explanation at all.  Their representative mentioned K1KP's article in the Nov
'95 issue of QST on using a optocoupler for T/R switching, but even he
acknowledged that the problem I was seeing didn't sound like a timing problem
with T/R switching.  This morning I contacted ETO Customer Service (Ray
Heaton), and he gave me what I think is a totally plausable explanation.
 This is that the 706 is actually putting out a momentary spike when it first
starts transmitting that is full-scale (or worse) output.  Some time delay is
required for the ALC circuitry in the 706 to kick in and cause the output
power to be cut back to the proper amount.  This time delay is in
milliseconds, of course, so a peak-reading wattmeter is not fast enough to be
able to record it.  The LEDs on the Alpha do show it, though, and Ray
suggested that I was risking damage to the PIN diodes in the Alpha if I
operated it with this initial spike coming down the line from the 706. He
suggested that what I really need to do is use a scope to measure the size
and duration of that leading spike and then go back to Icom with the
information.

This sounds fine, but I don't have access to a scope these days.  So, for
those of you with the perseverance to read this far, I wonder if there's
anybody out there with a 706 and a scope who would be willing to take a look
at this for me?  Alternatively, I'd eagerly be willing to go anywhere in the
SFO bay area to set up a test with my 706 if you have a scope we can use.

Bruce Sawyer, AA6KX

>From Larry Tyree <tree at cmicro.com>  Wed Feb 28 16:38:05 1996
From: Larry Tyree <tree at cmicro.com> (Larry Tyree)
Date: Wed, 28 Feb 1996 08:38:05 -0800
Subject: Next SquINT contest
Message-ID: <199602281638.IAA27069 at cascade.cmicro.com>

                       INTERNET SQUIRT CONTEST

The fourth SquINT contest will be held on March 9th at 2100Z for
for 90 minutes.  Suggested frequencies are 14270-14290.  Exchange 
name, age, QTH (ie: state/province/country) and favorite song.

There are three categories:

1. Parent-child category:  All transmissions must be made with real time
speech from the mouth of your child (sitting in or near your lap).   
Whispering in their ear is okay.  Logging done by the control operator.
Guest ops are okay.  So are guest parents.  Beware of third party rules.

2. Child operating and doing all the logging.

3. Child at heart operations.

Potty breaks do not count as off time.  Add 10 points for each diaper
changed during the contest (up to a maximum of 30 points).  The diaper
doesn't have to belong to one of the operators.  Pull-ups or Good-nights
do not count.

Final score = Number of minutes spent having fun in front of the radio
with your kid * the number of favorable comments you get from your 
spouse about the activity and then add the diaper bonus.

E-mail your logs and comments to kids at cmicro.com.  If you are not on this
list, please subscribe via n6tr at cmicro.com.  A test message has been sent
to the list.  If you didn't get it, then you need to subscribe.

There will probably be colorful certificates available to all particpants 
for a small fee to cover printing and postage (thanks to Greg, KO9Y).

Tree N6TR
tree at cmicro.com

PS: This is a real fun operating event...  don't miss it!!!!

>From sawyers" <sawyers at cacd.rockwell.com  Wed Feb 28 16:59:19 1996
From: sawyers" <sawyers at cacd.rockwell.com (sawyers)
Date: Wed, 28 Feb 96 10:59:19 cst
Subject: Re[2]: 80m + Rohn 25 in swamp = HELP!
Message-ID: <9601288255.AA825526788 at ccmgw1.cacd.rockwell.com>

I really hesitate to touch this one.

I do see two ways of doing this. One is a permanent installation, ie 
footings to something solid and wind loads and engineering ie. read 
expensive. To put up any permanent structure in a swamp, you need to get 
the footings down to something solid that will support the load, and will 
not freeze. This is for the footings for the tower. For the guy anchors you 
need something that will support the side load generated generator by the 
guy pull, and you need enough mass so that the concrete weigh minus the 
weight of the equivalent volume of swamp water and goo will resist the up 
lift component of the guy forces. 

You will need a soil analysis - runs a couple of K bucks, engineering time, 
then pumps to drain the water - maybe a coffer dam .... You get the idea.

The other is field day style. Small diameter push up pole and guy ropes 
tied to trees, with the understanding that this is a semi temporay 
installation in a clear fall zone. If a tree falls in the woods, who cares. 
If it falls on your house or your neighbors house then it is a much more 
significant problem.

This could be supported by a post driven in the ground with appropriate 
insulator.

Also don't go near this if the wind is blowing.

de n0yvy steve

My company and I agree on one thing - my opinions are my own.


>From k5na at bga.com (Richard L. King)  Wed Feb 28 17:07:26 1996
From: k5na at bga.com (Richard L. King) (Richard L. King)
Date: Wed, 28 Feb 1996 11:07:26 -0600
Subject: 160 Contests
Message-ID: <199602281707.LAA26107 at zoom.bga.com>

Here are my (K5NA's) comments on Daive's requirements suggestions:

>1 Each contest to last from "local dawn to dusk" not from 'x' hours Zulu

Not good, even though I knew you meant local dusk to dawn. That would give
more operating hours to areas further north than need the advantage least.
Daive, just because you are getting old, like me, doesn't mean that the
hours of your favorite contests should be shortened.

>2 Points based upon radial measurement from stations QTH.

I have always thought this was a good idea but near impossible to implement.
How about 5 points per QSO for contacts between CQ zones that are physically
touching and 10 points per QSO between zones that don't touch?

>3 Band split into 3, .....non participants....US EAST + US West.....DX....

I'm not sure exactly what you mean by this?

>4 DX to US qsos can only be between windows ie split freq only.

I am not necessarily in favor of this being the ONLY way of making DX to USA
QSOs. How about a window where only DX could transmit working only USA in
another window where only the USA could transmit. An example would be only
DX stations transmitting from 1830-1840 KHz and listening 1840-1850 KHz and
vice versa for USA stations. On the other frequencies (1800-1830 KHz and
1850-2000 KHz) all simplex QSOing would be allow, ie. DX/USA, DX/DX, and
USA/USA. The size of the windows could be downsized for the CW contests.

>5 Each organiser must appoint someone who's job is to tune the band logging 
>infringements. Disqualification rewards bad operating behaviour.

Bad idea. Who would want to do this even if there wasn't the potental for
legal problems to result. The only station I can think of that would delight
in this task might be WA4D.

>6 QSO must include serial number, lets reintroduce some skill into the qso

I really agree with this idea. The serial number was removed years ago in
this contest because it was felt that copying an exchange was too difficult
on 160 meters. At that time, the contest managers thought that just copying
the callsign was significant. Of course, this was before SUPER CHECK
PARTIAL. In addition to putting the serial number back into the exchange, I
would suggest that the contest manager also check for whether the stations
actually copy the serial number correctly. Otherwise, it is wasted. Only the
ARRL currently checks for correctly copied exchanges.

>Thats enough to begin with, I will await the shark attack...

No sharks here. Just an ongoing love of 160M contests.

>As far as packet and more recently internet spotting is concerned that is 
>something for general debate, I personally think that the word contest has 
>lost its meaning in the context of our activities...its hardly a contest if 
>you pit David against Goliath, no matter what the fable said, in the real 
>world the big guy wins.....So how far do we go to make more qsos than the 
>competition??   Answer...as far as the rules allow. What do we want to do 
>about this fiasco??

Years ago, before packet, I repeatly heard a few of the major single-op
competitors in the 160M contests being notified, by their friends, about the
presence and frequency of DX mults on the band. This was done on their run
frequency and was within the rules although I didn't like the idea very
much. Maybe I was jealous.

The packet spotting is the same thing. As long as the single-op operator,
himself, isn't using packet, then his friends are free to spot him every 5
or 10 minutes. Also it is standard practice for multi-op stations to
systematically go though the user lists on the PacketCluster network and beg
for QSOs using talk messages. The larger PacketCluster networks certainly
contribute to an advantage. I don't think there is anything you can do about
this and rulemaking to limit it would be a problem.

>Thouhts, ideas, grumbles and mumbles, lets hear it all and lets DO SOMETHING!
>
>Regards to you all, without you 160 would be really boring!! 
>
>Dave AA0RS / G3SZA

I have never thought a 160 contest was boring. I did some of my best reading
at noontime while listening to the CQ button repeat itself.

73, Richard
K5NA at BGA.COM


>From H. Ward Silver" <hwardsil at seattleu.edu  Wed Feb 28 17:12:03 1996
From: H. Ward Silver" <hwardsil at seattleu.edu (H. Ward Silver)
Date: Wed, 28 Feb 1996 09:12:03 -0800 (PST)
Subject: 80m + Rohn 25 in swamp = HELP!
Message-ID: <Pine.3.07.9602280902.E2049-a100000 at handel.seattleu.edu>

I would think that there might some serious settling problems once the
base is poured.  Can you get to a firm soil layer within 6-feet of
surface?  It might a REAL GOOD idea to check with a contractor or soils
engineer for a little advice (not necessarily a soils/footing design)
about the ability of the subsurface material to support the load. 
Otherwise, you might see your tower sink slowly into the ooze...not kidding!

73, Ward N0AX (son of an expert soils engineer who saw too many disasters
on field trips with Pop)



>From H. Ward Silver" <hwardsil at seattleu.edu  Wed Feb 28 17:34:21 1996
From: H. Ward Silver" <hwardsil at seattleu.edu (H. Ward Silver)
Date: Wed, 28 Feb 1996 09:34:21 -0800 (PST)
Subject: 80m + Rohn 25 in swamp = HELP!
Message-ID: <Pine.3.07.9602280920.L2049-b100000 at handel.seattleu.edu>

If you rely on the weight of the base to settle itself, two things will
happen.  The first is that it will settle progressively over a LONG period
and may actually bob up and down depending on water content of the stuff
under the base.  Second, and most dangerous, is that it will settle
unevenly, making your new Rohn the Leaning Tower of Whizzer!  Without a
proper footing, I would bet money on both happening.

I suggest that you talk to local contractors and ask them what they have
done for other jobs in the area under similar soil conditions.  The usual
method for buildings is to drain the area (if possible and permissible),
then put in several deep cores by drilling holes and filling with
concrete.  Then a crushed rock pad is put down and the concrete foundation
put in over that, tied to the cores.  Expensive!

I take it that the idea is to put up a vertical in the swampy area?  I
think the concrete base idea is going to be either too expensive, too
difficult, or too risky if done on the cheap.

Why not consider a more flexible, lightweight structure made from
irrigation tubing or EMT?  A tripod-like affair mounted on a pad made from
pressure-treated 4x4's or railroad ties could be anchored in the swamp and
guyed.  The pad could be anchored to trees or long stakes driven into the
ground (rebar? galvanized pipe?)

73, Ward N0AX