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Author Topic: Im puzzled!  (Read 3163 times)
KT4DLB
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Posts: 76




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« on: May 03, 2013, 08:04:48 PM »

I put up a new Hustler 5BTV antenna 10 foot off the ground and radicals yet. I notice on CW when sending, the power reading for the radio drops from 13.8 volts to around 12.5 volts dc. Is this norml? Also it seems like there is a ground hum on the radio now I can hear in my headphones. The grounding system wasn't mess with. I went from a G5RV to this Hustler. Any suggestions

Lamar
KK4NZO
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KB4QAA
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Posts: 2381




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« Reply #1 on: May 03, 2013, 09:11:21 PM »

Power supply voltage is an issue with your power supply and the radio.  It has nothing to do with the type of antenna or whether you have radials.

-Voltage measurements should be taken at the radio terminal connection.

-Maximum current draw will occur when in a continuous mode like CW, AM, FM or RTTY.

-Check and clean your connectors.  For molex connectors or other plugs, spray a little tuner cleaner/Deoxit and seat/reseat several times to scrub any oxidation.

-Don't forget to open up and clean any inline fuses.  They build up corrosion too and we never think to check them.

-What radio are you using?

-What brand, model and Amperage rating is your power supply.
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N0SA
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Posts: 15




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« Reply #2 on: May 04, 2013, 05:00:13 AM »

I would test my radio and power supply by running it into a dummy load.
If all works well then I would see if you are possibly getting RF interference
into your radio and power supply. If that is the case then you would need to
rework your grounding system.
Larry
n0sa
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K1CJS
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Posts: 6034




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« Reply #3 on: May 04, 2013, 08:27:48 AM »

The last thing KB4QAA mentioned would be the first one I would check.  If you're running a power supply at it's capacity--or over it--the conditions you specify would be the result.  Also check every single connection from that supply to the rig, even where the wires transition to the fuseholder clips.  If the power supply rating is large enough, sufficient voltage drop could well develop over a single bad connection.  A quick way to check that is to feel the connections--a bad connection will most often heat up after a bit of use, heat being the way the power used is being dissipated.

Does your rig still exhibit the same symptoms if you use a lower power level?  If it doesn't, then you have a power supply problem somewhere.  Another thing to check--although unlikely-- is that the power supply is developing a fault.  Try running with a different supply or a battery to check that.  Good luck and 73!  
« Last Edit: May 04, 2013, 08:34:19 AM by K1CJS » Logged
KT4DLB
Member

Posts: 76




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« Reply #4 on: May 04, 2013, 05:04:45 PM »

I'm leaning toward rf interference. New power supply and radio. Both were fine until antenna change out. But on 10 meters the voltage doesn't drop at all. The swr on 15 and 40 meters is 1.1 to 1.5. When sending CW, I'm using the West Mountain Plug n play to send and recieve. Before the antenna change out had no problems. Do I need to run a ground wire from the antenna to a ground rod say right next to antenna? Thanks for all the help so far.

Lamar
KK4NZO
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WB6BYU
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Posts: 13287




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« Reply #5 on: May 04, 2013, 05:28:39 PM »

Quote from: KK4NZO

I'm leaning toward rf interference....



Do you have quarter wave radials for 15m and 40m connected directly to the base of the
antenna (NOT to the base of the mast)?  If so, how many radials for each band?

If you don't, then add at least two, preferably 4.  They can be horizontal or sloping
downwards as long as they don't get too close to the ground.

Then add an RF choke/current BALUN in the coax near the base of the antenna.  That
helps to prevent RF flowing back down the outside of the coax, which is the most
common source of "RF in the shack."
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KT4DLB
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Posts: 76




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« Reply #6 on: May 05, 2013, 03:51:59 PM »

What rf choke/balum would you recommend. DX Engineering has one that sells for about $135.00. I going to try and run some radicals for 15 and 40 meters.

Lamar
KK4NZO
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WB6BYU
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Posts: 13287




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« Reply #7 on: May 05, 2013, 06:43:36 PM »

You can do it a lot cheaper than that.  Got to G3TXQ's page here:

http://www.karinya.net/g3txq/chokes/

and choose a design for an air core choke (just some coiled up coax) that is effective
on a particular band where you have a problem.  (Note that chokes made from coiled
coax have a fairly narrow window of maximum effectiveness, but may still provide some
help outside that range.  You can add two of them in series spaced a couple feet apart
if needed.)   That way you can see if it actually helps to eliminate the problem before
investing in a commercial one.

But the first step is to add the radial wires to the antenna feedpoint:  that alone may be
enough to fix the problem.  If not, then try the choke approach as well.  MFJ makes
a wideband feedline choke for something like $40 that may work once you've tried the
air core type to see the improvement.
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K5LXP
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Posts: 4492


WWW

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« Reply #8 on: May 06, 2013, 06:11:54 AM »

Another step I would do is to determine at what power level the symptoms you experience start.  Let's say for example everything works as expected until you hit 50W, where the supply current may dip or you hear the hum in the headphones.  Then you implement a fix, like an air choke.  Run the test again and see if the point where the problem starts changes, or stays the same.  That will tell you if you're on the right track or not.

Mark K5LXP
Albuquerque, NM

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KT4DLB
Member

Posts: 76




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« Reply #9 on: May 06, 2013, 10:50:07 AM »

You can notice it starts at about 50 watts and up. I can drop it down below 50 watts and the power supply voltage will stay at 13.8 volts dc. When you get above 50 watts then the voltage will start dropping as you go up on the watts then the voltage will continuely  drop till its about 12.6 volts dc.
On the other comments, the choke at MFJ that I found are the chokes that you place around the coax. Is this what you were referring to? I like the price of them compare to the rf choke that DX engineering has.


Lamar
KK4NZO
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N4CR
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Posts: 1668




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« Reply #10 on: May 06, 2013, 11:21:22 AM »

I'm still inclined to think you have a problem with the power supply.

Why after the antenna change, you ask? If the old antenna was a poor match, your radio could have been folding back power to protect itself, thus never reaching full output.

Now, you have a good load and the radio produces full power, stressing the power supply.

Try transmitting into a dummy load to see if the problem persists.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
K0ZN
Member

Posts: 1548




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« Reply #11 on: May 06, 2013, 07:05:56 PM »


 Please give more information on exactly HOW and WHERE your radials are connected and how LONG they are and how MANY of them there are.
 What kind of coax and any relevant details about the line and connectors, etc. How far away is the antenna from your radio?
 Without this info it really just a bunch of wild guesses to help you.

 The suggestion to try the rig into a known GOOD load such as a dummy load is very good/important. With a good dummy load you know it is truly
 non-reactive and the radio will be "totally happy". That is not the case with any antenna. The dummy load also will NOT radiate and cause issues.
 
 Bottomline:  start the troubleshooting in a logical sequence, rather than just throwing money at it and changing components.

73,  K0ZN
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N6AJR
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Posts: 9908




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« Reply #12 on: May 08, 2013, 10:43:46 AM »

First off, what type ( linear or switching) and current rating (20 amp, 30 amps etc) of the power supply are you using. A typical 100 watt radio needs about 1 or 2 amps at 12 v in receive,And between 22 and 25 amps at 12 v on transmit , full power , in FM, rtty, cw,  and on voice peaks on ssb. A typical power supply is rated 20 amps peak, 18 amps continuous, which causes voltage drop on transmit, if the radio is looking for 22 to 25 amps. 12 volts here is what we refer to but it is truly 13.8 volts for a 12 volt supply. so if you buy a supply for a 100 watt transceiver, then spend d the money and get a 30 or 35 amp supply and this problem goes away, or operate you radio at reduced  power out like 50 watts  to draw less current. once the voltage starts dropping due  to not enough current capacity, all kinds of weird stuff happens.  This does not mean that you are not getting RF back in the  radio, but is the first place to look.
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KT4DLB
Member

Posts: 76




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« Reply #13 on: May 08, 2013, 02:09:22 PM »

The power supply is a Jetstream switching supply and its 25 amp continuous and 30 amp surging. The power stays the same on the power supply if the radio is transmitting at 100 watts or 25 watts on CW or voice.
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KT4DLB
Member

Posts: 76




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« Reply #14 on: May 09, 2013, 01:54:07 PM »

Well I put the rf chokes on at the base of antenna and run some radials. Still the same problem with the power dropping at the radio on 80, 40 and 15 meters. 10 meters is ok and 2 meters is ok. So I don't know what else unless it is the power supply.

Lamar
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