Re: [IC-7000] What is typical IC-7000 output/SWR question


Steve W3AHL
 

The key to determining if excessive voltage drop is causing the TX power drop & fluctuation is to measure the voltage on the TUNER port, pins 3 & 4 (14 VDC & GND, nearest the edge of the case) while transmitting at 100% TX PO setting into a dummy load. This will show what the voltage is INSIDE the radio. Measuring TX power output versus power supply terminal voltage won't show if there is excessive voltage drop at all the crimps, fuse holders, connector at the 7K, etc.

I believe you said you had cleaned the oxidation off of the fuses, but that is not a good solution. The factory fuse holders should be removed and either replaced with good quality automotive style holders (preferably with #10 gauge wire pigtails, not #12)or just use a RigRunner for DC distribution. Its not that a 6" pigtail of #12 wire will cause excessive IR drop, but the ones made with #10 typically have heavier blade contacts and a better connection of the wire to the contacts.

The goal is to have less than about 300 millivolts drop from the battery/power supply terminals to TUNER port pins 3 & 4 under full load. Yes, this is attainable.

Your problem is not SWR foldback. That doesn't start until 2.5:1.

I have never seen "RF feedback" cause a reduction in power in the 7K, although there's always a first for everything. Usually it will manifest as an ALC reading that is much higher on certain frequencies or bands, due to inbalance in the antenna elements and an inadequate common-mode choke on the feed line at the feed point of the antenna (not at the radio, preferably). Poor feed line connections can cause similar problems. Also, a poor RF ground to the shack can cause the SWR and power meter readings to fluctuate.

For ferrite chokes to be effective at HF you need to use Fair-Rite Type 31 chokes or Type 43 could be used above 20M. They need to be large and have multiple turns of wire/coax through the core.

Finally, Astron switching power supplies often have rapid voltage fluctuations under dynamic load that won't show on a DVM. A common fix for this is to make sure that all screws holding the main PCB to the case are tight. I remove the screws, remove the PCB, verify ther is no paint or other contamination on the mating case surfaces, then reinstall everything, putting external-tooth lock washers under all the screws holding the PCB to the case. Tighten firmly and recheck in 6 months. They can also be sensitive to ground loop RF currents if your RF ground isn't properly bonded to the electrical panel ground.

But in probably >80% of the cases that I've seen, your symptoms are typical of excessive voltage drop on the DC supply cable.

Regarding the post below: 100% power output is factory calibrated to be 95 watts at 13.8 VDC input. It is limited by the APC circuit to 105 watts max in a correctly adjusted radio (as opposed to one that someone has "tweaked"). But most good power meters' accuracy is +/- 5-10% at best across the bands, assuming a high quality dummy load and good coaxial jumper. I've never seen a factory adjusted 7K put out 115 watts into a calibrated analyzer (Agilent 8924C with a Narda 30dB attenuator). Power output will certainly vary with a change in load impedance, especially into a reactive load like an off-resonant antenna, since reactance doesn't absorb power like resistance. This not the same as the power "folding back" due to a protective circuit increasing ALC, which reduces gain to the IF stages feeding the driver.

But as the poster's measurements show, it doesn't account for your drop to less than 80 watts. That's why only a dummy load can tell if there is a problem with your radio, which I would guess there isn't.

Steve, W3AHL

--- In ic7000@yahoogroups.com, John Kramer <jkramer@...> wrote:

Craig

Right, I pulled my spare 7000 out the closet and did some tests, here are
the results:

Band tests were done on: 40 meters
- At 13.8 volts I reached max forward power - 115 watts
- When I start lowering the voltage, power starts to drop off immediately from 13.7 volts and below,
however it is a very gradual drop. I have to get down to 12.76 volts before it drops (from 115 watts)
down to 100 watts, and then drops rapidly if the voltage goes below 12.76 volts
- SWR - yes it is very sensitive. At 1.1:1 and 1.2:1 it is at full 115 watts. It starts to drop off on output power
from 1.3:1. When I introduce an SWR of 1.6:1 the power has gone down to 100 watts (from 115 watts)

So in conclusion, as long as your SWR is below 1.5:1, and your voltage is above about 13 volts, you will get
more than 100 watts out the rig. 13.8 volts and an SWR of below 1.2:1 will give the full 115 watts.

That is on my 7000, this one bought in the USA about 2 years ago

73
John, ZS5J






On 06 May 2013, at 6:13 PM, John Kramer <jkramer@...> wrote:

Craig, you are right. If it is starting to fold back at an SWR of 1.2:1 or 1.3:1, then
that does sound over sensitive. I have not checked mine, but I would think
that it only starts to fold back on power after 1.5:1. I will do some tests and let you
know at what point it starts to cut back.

Regarding sensitivity to voltage, yes, it is very sensitive, but 13.8 volts should be
plenty for full output. I will also do some tests to see at what voltage my 7000's
start to drop in power. I do know that the 7000's that are in my mobiles, they run
at reduced power output when my vehicle is switched off, or when the alternator
is not charging. I can immediately see when the alternator kicks in, as the power
bumps up….although it doesn't bother me too much, I use it as it is. Some guys
have bought the MFJ gadget that goes in line with the power cables, and keeps
the voltage at a steady 14 v regardless of wether the alternator is on or off.

From a happy owner of 3 x IC-7000's

73
John, ZS5J




On 06 May 2013, at 5:25 PM, Craig Pitcher <cpitcher@...> wrote:

Jim and Milo,

Thanks for your comments. I think my real question got lost. What I was
asking was is it normal for the 7000 SWR power reduction feature to reduce
the power so much when the SWR only goes from 1.1 to 1.3 to 1? Seems like a
reduction of 20-25 watts at that kind of SWR is excessive. I could
understand this if the SWR was high, like 1.8, but 1.2 or 1.3 is a decent
SWR, and as good as you can get on many antennas..

To Milo's point about an extra 5 watts or so does not make much difference
is true, but an extra 20-30 is the difference between being heard, or not
heard by a DX station.

I made the comment about voltage as a result of reading several posts on the
7000 needing higher voltage than the 13.8 that my power supply was set to
produce.

For the record, I use a Bird 43P with a 100 watt slug (peak reading meter),
and an RF Applications P-3000 computerized SWR/Wattmeter. They read within a
few watts of each other.

Thanks, but I still don't know whether the power reduction is typical or if
mine is over sensitive.

Craig

-----Original Message-----
From: ic7000@yahoogroups.com [mailto:ic7000@yahoogroups.com] On Behalf Of
Milo Austin
Sent: Monday, May 06, 2013 7:04 AM
To: ic7000@yahoogroups.com
Subject: Re: [IC-7000] Re: What is typical IC-7000 output/SWR question

Hi Craig,

I'm going to go out on a limb here, so forgive me ahead of time if I sound a
little harsh. Several good and important points have already been covered.
But what jumped out at me was your statement that you didn't know what your
car's alternator put out. Now I'm not saying that this information is
terribly important in this case. What I am saying is that this seems to
indicate a lack of very basic skill and understanding.

Maybe instead of focusing on squeezing out the very last watt, you should
focus on the fundamentals. And one of those fundamentals you should already
know is, if you are transmitting at even 75 watts, or especially 96 watts
instead of 100, the person at the other end is NOT going to be able to tell
one bit of difference. I don't have the figures in front of me, but the
difference in power received versus the small change in transmit power is
negligible. It's pretty much accepted if you can get even 1.3 or better
VSWR especially from a mobile antenna and over a range of frequencies,
consider yourself lucky. If you really want to squeeze the best SWR from
your antenna, start looking at a means to match your antenna, not upping the
voltage to 14.

As a rule, I never run my 7000 at full power, though it certainly is
laudable to look for the best possible efficiency (lowest SWR) regardless of
the power level. The less concern you have about that last 5 watts is the
longer your finals will last also. Operating mobile tends to increase the
chance for unknown or uncontrolled circumstances that might prove
catastrophic at maximum power. And always, ALWAYS check your VSWR at a much
reduced power first, the lowest power that will produce a reliable SWR
reading, since you have no clue for sure what it is going to be. And if you
need to do extensive antenna testing, invest in an antenna analyzer and save
the world from having to listen to your whistles across the band.
Much less than 100 (even 5 or 10) watts can be heard around the world under
the right conditions.

73, Milo
KF5GCF

On Mon, May 6, 2013 at 12:26 AM, Jim <w8lgz@...> wrote:

**




Hi Craig,

You don't mention a couple points needed to help with your problem;
that's what mode you're using, and what type of meter you're using to
test.

First, never try to get an accurate reading of your radios power out
into an antenna (Unless you know for fact you have perfect VSWR and
little to no loss on the feed line, which almost never happens in most
installs; always use a 50 Ohm dummy load.

Second, you should (for ease of testing and to get a proper reading)
always use CW mode to get a fairly accurate measurement (most meters
have a 5%-10% tolerance +/-). If you have performed your tests in CW
mode and are showing 96 watts as you said, I wouldn't worry about it.
If you're testing in SSB and showing 70-80 watt peaks on an average
reading meter (should always use a quality peak/hold meter for SSB)
again, I wouldn't worry about it. Chances are very good your radio is
producing proper power out.

Jim, W8LGZ


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