As many times you will read from my posts that a dedicated ground should
exist between the power supply ground and the radio ground. Although
Denton seems to confirm adding a ground did correct his concerns, I have
found in some cases it does not. In other cases it does improve RFI issues.
What I typically find can be confirmed by using a DVM and measuring the DC
voltage between the power supply ground and the radio ground. In transmit
mode, CW key down, the transmitter is drawing maximum current. By measuring
the voltage between power supply ground and the radio ground one can then
determine just how much above ground, i.e. the zero volt point, the radio
exists above ground. Typically I find anywhere from 0.125 to 0.250 volts to
be the value. By adding a dedicated ground between the power supply ground
and the radio ground this value drops to near zero volts. Although the
current is much less in receive, the amount of effective series R exists in
both receive and transmit.
In most cases today the DC negative and the power supply ground are
connected at some point internal to the power supply. Some may agree this
is correct and some may disagree. Personally, I prefer to have DC negative
and power supply ground to exist at a common point inside the power supply.
Also this is the same point where the 3rd pin AC ground is attached. I also
suggest one investigate to assure that the method of attachment is not
electrically violated by paint on the chassis. If you suspect such, just
lift the connection point, use a bit of #100 sandpaper and remove the paint
around the attachment point until bare metal is exposed. Then using proper
hardware, which includes an internal tooth lock washer to bite into the
metal, reconnect the DC negative, the chassis ground and the 3rd pin AC
ground. And while you have the cover off, check to see the upper part of
the cover and the lower part of the cover again are not insulated from each
other by paint. Just clean it off where the screw holes are located on the
inside edges and again use an internal tooth lock washer as part of the
assembly process. This assures the covers are electrically connected.
If you have a switching supply that causes noise, the above may correct all
of your concerns.
73
Bob, K4TAX
----- Original Message -----
From: "denton sprague" <denton@oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, September 02, 2014 12:36 PM
Subject: Re: [TenTec] TT 940 Power Supply
Ok….I installed a no 10 wire between power supply and Omni 7….that seems(?)
to have cured the problem.
No chopped the 3rd pin ground….I got everything in the shack tied to a
industrial grade sine wave ups running on a dedicated 20 amp circuit.
speaker is on the right of the rig….also have a little astron ss30 and a
huge astron 50m linear power supply that I used to use for entire station.
No rf hash for any of the laptop chargers so far…
On Sep 2, 2014, at 10:13 AM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
wrote:
Do you have a solid ground wire between the supply and the radio? If not
the radio is about 1/8 to 1/4 volt above DC ground.
You haven't chopped the 3rd pin ground have you? For safety reasons, it
must be in place.
Some have reported with the supply on the left it makes noise, on the
right it does not. I may have my left's and right's reversed. Anyway, I
think you get the idea.
The ONLY noise I have from a switching supply is from the charger for my
laptop computer. I've purchased three different ones. All produce noise.
As to the station supply, I use Astron SS-30M's or SS-25's. Have three
and all are quiet.
73
Bob, K4TAX
----- Original Message ----- From: "denton sprague"
<denton@oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Tuesday, September 02, 2014 10:43 AM
Subject: Re: [TenTec] TT 940 Power Supply
Well darn…
my 940 has a traveling growling noise on 80 meters….wonder if there is an
easy fix?
Otherwise will sell the darn thing….
On Aug 29, 2014, at 11:36 AM, Ralph Arnold <rea.papaof10@gmail.com> wrote:
I'm interested in PS for my Pegasus will it handle it and how much $$ 73
KD8BTQ Ralph
On Fri, Aug 29, 2014 at 1:17 PM, Charles J. Nagel <cnagel@sbcglobal.net>
wrote:
I have four TT switching power supplies I use for various rigs including
Ten-Tec and Elecraft. Never a noise issue. One is a recently acquired
940,
a perfect match for the Omni VII, in my opinion.
Charles, K0CW
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|