What is an acceptable voltage range rx to tx?

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  • Updated 1 year ago
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I am powering my 6500 with an Astron 70-m using the factory supplied power cable. When monitoring the voltage with K9DUR's SDRMonitor  I see a RX voltage of  12.59 and a TX voltage of 13.45.
Is that spread acceptable?
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kd5foy

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Posted 1 year ago

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Bill -VA3WTB

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I am surprised the voltage is not dropping on transmit. Many run around 14v.
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Zack Schindler - N8FNR

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This link shows how to adjust the output power on an Astron PS.

http://www.repeater-builder.com/astron/voltage-adjust/voltage-adjust.html
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Craig Williams

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I had to switch to an Alinco DM-340MW as my non switcher Astron would not adjust high enough to work with my PWRgate and an AGM battery. With my Flex 3000 I see 14.0V on RX and 13.5 on TX, full power, with the 2 tone test. I am loosing 0.3 volts between my Rigrunner power pole strip and the meter on the 3000 software. I am surprised as there are 2ea #12, 1 foot wires between the Powergate and the Flex power connector. That's 4 watts which seems a little high but, 97 watts PEP is as good as 100 watts PEP so thats good enough for me.
(Edited)
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Bob Gerzoff, WK2Y

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I think the specs call for 13.8 +- 15% which would allow you to get down to 11.7 V and still operate. I use an Alinco pwr supply and  see about the same drop you do when running directly to the rig under full transmit, 15.4 amps.  .  I did some testing and did notice a drop in maximum output power with the lower voltages.  Though the watts seem important, the decrease translated into a 0.4 db difference in output.  At least in my shack, each set of PowerPole connectors results in a 0.2 V drop.  I have about an eight foot run of 12 gauge and two sets of power poles.  If your pwr supply is adjustable you can set it to 15 and squeak out a few additional watts if you want and you can go to number 10 if you feel compelled. 
73
Bob
WK2Y
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Bob- W5TX

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Are you sure you got the numbers correct? RX voltage should normally be higher than TX voltage due to increased drop when transmitting. If you did interchange the numbers may be normal depending on your supplies no load voltage.


Bob W5TX
(Edited)
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NX6D Dave

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If the numbers are correct, I would take a close look at the power supply.  It sounds like it boosts the output voltage as the current goes up, which would make the regulator circuit looks suspicious.

I also use an Alinco.  It supplies constant voltage as the current goes up from 1 amp or so when the radio is idling, to about 15 or so when transmitting.  Measured at the PS, the voltage is constant.  Measured at the radio, the IR drop takes about 1/2 a volt off the delivered voltage.  I recently boosted the output voltage a little to take up this slack.  The PS is capable of 32 amps, so it's running at it's mid-point.
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Justin - KL2D

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I have just been tinkering with this today, as I was reading a thread about a power drop on a 6300 and have been experiencing something similar with my 6700. I hadn't really worried about it for a while, but it started nagging at me, and I started fiddling... you know how it goes. hi hi 

Anyway, I shortened some of the power cable runs to my rig runner and from there to the 6700. That helped a tiny bit, but not much. I also have a RS-70M power supply, and can confirm that there is not voltage drop from it on transmit at the supply, the thing is a beast. I do see a voltage drop at the radio however, I was reading 13.11V idle and 12.23 during transmit using K9DUR's meters. I was reading 13.85 out at the posts on the back of the RS-70M with a Fluke multimeter. 

A quick google search reveals a trim wheel on the circuit board inside the RS-70M. Most Astron supplies have this. I disconnected it from all power draws, and put the Fluke back on it. I adjusted the trim wheel to get 14.6V out at the posts with no load. Now I am 13.8V idle and 13.4V using K9DUR's meters. 

So, depending on what all you have running off the power supply, you could turn up the voltage a bit and probably resolve your issue. This worked really well for me. At least for now, and of course YMMV. 

Best of luck!

73

Justin
KL2D
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ka7gzr

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Sounds like RF getting into the power supply/metering circuits.

Jim

ka7gzr

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Tim - W4TME, Customer Experience Manager

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Official Response
The radio needs to have 13.8 VDC at the radio on transmit (under load at full power).  I would expect some IR (voltage) drop due to contact resistance, length of the power cable and if you are using a fuse/distribution block.  You may have to increase the supply output voltage to compensate for the IR drop.

You do not want to exceed 15 VDC st the radio.
(Edited)
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Rich McCabe

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I have found it hard to maintain TX voltage with substantial wire length, power pole connectors and rig-runners. I have my main rig runner near back of Flex and power it with two pairs of 10 ga wires from 50 amp supply. Then the Flex to the rig runner is only 2' long.  Works well.

My first 6300 Flex was not happy with 10" of heavy cable and rig runner in middle. Would only do about 85 watts.
(Edited)
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Stan - VA7NF

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The best arrangement continues to be a 12V battery connected directly to the power connection with at least 10 gauge wire.  This battery is then charged at a steady rate.

A 15A PS can maintain a 7Ah - 150Ah battery except in the heaviest draw (e.g. a 12 hour 100W RTTY contesting)
Only condition is the internal resistance of the battery
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Craig Williams

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I cheat. My 100AH AGM battery puts out 14.0 VDC. At the other end of my MFJ-4416C battery booster.
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ka7gzr

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Really depends on the chemistry of the battery to understand voltage and current (power) available at the input terminals of the Flex .The typical lead acid battery under load will stabilize at 12.5 Vdc which will not support 13.8 Vdc at the Flex terminals. Output power of the Flex will be less than the rated output because of this. NiCad's and Lithium Ion are a different chemistry for charging and load voltage/current.  

In the end the best bet is the largest gauge wire, good terminations and shortest lengths of wire from the power source to the Flex.

Jim

ka7gzr 

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Pat - WH6HI

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One way to insure proper voltage at the terminals of the radio, is to have a power supply that has a sense wire attached to the input terminals of the radio. I use such a power supply and radio stays +- one tenth of a Volt at 13.8 volts. They cost a bit more, but worth the price for such an expensive radio.

Pat
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Pat - WH6HI

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I use the B&K Precision Model 1900 rated for 60A max current, but best operation max is 50A.  And, yes it is a lab or bench power supply.  Very clean and very happy with it.  
(Edited)
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Bob Gerzoff, WK2Y

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I have never heard of such a unit.  Sounds very useful.   Do you have any specific names/models?
73, 
Bob. WK2Y
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Michael Walker, Technologist

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At time, the powerpoles can become slightly oxidized and it is worth cleaning them with something like a pencil eraser.  It doesn't take much to loose a volt or 2.  Remember ohms law?

Like Tim said, you can run up to 15V into the back of the radio.

Mike
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Tim - W4TME, Customer Experience Manager

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I clean my PowerPole contacts with DeoxIT Red and a q-tip then coat them with DeoxIT Gold.
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Craig Williams

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Just a note and before I forget good luck on your medical issue. I HATE power poles but use them because with the fused power strips it's easy to change up your shack which I seem to do all the time and all the ECOMM people use them. I say HATE as I never had to clean a butt connector or a spade lug tied to a terminal strip. A heck of a lot cheaper also. Someone at a Yuma said first responder's use them in their vehicles. Well, not in San Diego County and I bet nowhere. Terminal strips and soldered spade lugs. Even then in a fire truck you better tighten the terminal strip on a regular basis. Just saying.
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Tim - W4TME, Customer Experience Manager

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Thanks, Craig.

They are not my favorite either, but they are universal, prevent accidentally reversing the polarity and I have gotten good at making them.  I would not recommend them for an environment where vibration is expected.
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KC2QMA_John

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"I clean my PowerPole contacts with DeoxIT Red and a q-tip then coat them with DeoxIT Gold."

Pardon me can you pass the grey poupon :)

For most the Power Pole connectors work fine but I would have liked to see Neutrik powerCON  power connectors on the new radios. After all when you have the best radio on the market today why skimp on the main power connector.
http://www.neutrik.com/en/audio/powercon/
(Edited)