Previous in Forum: Electrical Design for Large Building   Next in Forum: Connecting a Hooter with Output Contact of an Ammeter
Close
Close
Close
53 comments
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71

Mystery Ohms

09/21/2014 11:59 AM

I have approximately 100ft of RG6 (75 Ohm) coax open at both ends.

I'm measuring with a cheap analog multimeter.

I'm connecting the leads between the shield and center conductor at one end.

Meter set on X1K scale the meter shows no movement (infinity).

Meter set to the X10 scale I read 50 on the Ohms scale, which I believe is 500 Ohms on that scale.

So what's happening with this open line?

Is it long enough that it's acting like an antenna or something?

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#1

Re: Mystery Ohms

09/21/2014 12:12 PM

Meter set on X10 scale the meter shows no movement (infinity).

Meter set to the X10 scale I read 50 on the Ohms scale, which I believe is 500 Ohms on that scale.

So what's happening with this open line? Operator error?

Register to Reply
Active Contributor

Join Date: Sep 2014
Posts: 10
#50
In reply to #1

Re: Mystery Ohms

09/26/2014 12:17 PM

Hello lyn;

First of all don't confuse impedance with resistance. Antenna wire is measured in AC Ohms (i.e. 75 AC Ohms). Even though both use ohms as the unit of measurement impedance is an AC measurement. Most DVM's use DC provided by the internal battery. Different scales on a DC VOM will give you a different reading due to the internal scaling resistors and the core insulation of the antenna wire plus a few other factors like the length of the cable. Usually antenna wire is rated in pico-farads per foot or meter. (i.e. RG 6 is about 16 pf per foot). The capacitance is what primarily effects the DC VOM. To correctly measure antenna AC resistance, use an AC Impedance meter and cut the wire to length to match your transmitting bandwidth.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#51
In reply to #50

Re: Mystery Ohms

09/26/2014 1:32 PM

One of the "tricks" in using 75 Ohm coax, with this type of horizontal loop, is to do just that. You cut a length of 75 Ohm cox to 1/4 wave length of what you plan to operate the loop on, 40 Mhz for example. Use that between the loop and the tranceiver, as an impedance match to the antenna. I my case I use 75 Ohm all the way from the tranciever to the loop and don't woory about the impedance match, as I do that with an antenna tuner across many bands rather than just one.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Active Contributor

Join Date: Sep 2014
Posts: 10
#52
In reply to #51

Re: Mystery Ohms

09/26/2014 2:14 PM

Hi Tom;

The loop trick usually works very well. Sometimes is low wattage transmitters a loop that is too big can effect your ERP (effective radiated power) even with a matched impedance and low SWR.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#2

Re: Mystery Ohms

09/21/2014 12:12 PM

Just corrected this so it reads correctly with X1K rather than X10.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
2
Guru

Join Date: Apr 2010
Location: About 4000 miles from the center of the earth (+/-100 mi)
Posts: 9629
Good Answers: 1098
#3

Re: Mystery Ohms

09/21/2014 12:14 PM

Sounds like you have a faulty meter.

Register to Reply Good Answer (Score 2)
Guru

Join Date: Feb 2011
Posts: 7025
Good Answers: 206
#4

Re: Mystery Ohms

09/21/2014 12:33 PM
Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21024
Good Answers: 791
#5

Re: Mystery Ohms

09/21/2014 12:42 PM

Weird. If it reads 50 on x10, it should be almost zero on x1k.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#7
In reply to #5

Re: Mystery Ohms

09/21/2014 12:46 PM

Zero would be continuity or a dead short would it not?

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#9
In reply to #7

Re: Mystery Ohms

09/21/2014 12:51 PM

Zero is nil. Dead short would be full scale deflection on Ohms setting.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#17
In reply to #9

Re: Mystery Ohms

09/21/2014 3:10 PM

On my meter, you ZERO the Ohms scale by touching the leads (continuity) and adjusting the needle until it's on ZERO, on the far right of the Ohm scale. On the far left of Ohm scale it reads infinity, or no deflection of the needle. So that's why I say ZERO is continuity.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#19
In reply to #17

Re: Mystery Ohms

09/21/2014 4:38 PM

Right. My mistake.

Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#8
In reply to #5

Re: Mystery Ohms

09/21/2014 12:48 PM

I think that's what he said. I agree, seems OK to me.

The value won't change if one changes the scale. The needle deflection will.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#6

Re: Mystery Ohms

09/21/2014 12:45 PM

OK so it sounds like it's time to go get the new digital meter...had a good one until it "went bad". Heavy equipment falling on meters tends to make them go bad!

I've been using the analog mostly to test continuity and voltages...no issues until now! Sorry the original post had that typo.

I'll let you know what the digital one shows.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Sep 2009
Posts: 1055
Good Answers: 88
#10

Re: Mystery Ohms

09/21/2014 12:56 PM

I've seen leaky cables before, but before jumping to that conclusion, make sure that ends are cut cleanly and are completely DRY, your meter is functioning OK on X10 scale, and that you are not actually metering some rectified RF from a 75 ohm coaxial cable posing as.. antenna. It happens with analog meters, since a diode is used parallel to moving coil for protection. Does value change with cable orientation? S.M.

__________________
Life is complex. It has a real part and an imaginary part.
Register to Reply
Guru

Join Date: Apr 2008
Location: Chicago
Posts: 3990
Good Answers: 144
#11

Re: Mystery Ohms

09/21/2014 1:12 PM

I'll guess that I've run and terminated hundreds of thousands of feet of RG6, SCCRG6, RG6QS and the like, but I've never had a reason to measure it resistance in Ohms. It's pretty much bullet proof when used for it's intended application.

I even invented a termination tool for the stuff..

__________________
High Tolerance is Beautiful
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#12
In reply to #11

Re: Mystery Ohms

09/21/2014 1:15 PM

Nice work!

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#13
In reply to #11

Re: Mystery Ohms

09/21/2014 1:25 PM

Nice work but I'm using PL259 connectors for an amateur radio antenna application.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#14

Re: Mystery Ohms

09/21/2014 1:53 PM

It depends upon your soldering skills. Too much heat, solder, rosin, etc. can yield a bad connection, but what you describe is odd. Try putting a known value resistor (dummy load if you have one) across one end and measure on different scales at the other end, they should all read the same.

An open piece of coax acts like a capacitor, so you have to be sure that you allow sufficient settling time for the meter's battery to charge it fully.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#18
In reply to #14

Re: Mystery Ohms

09/21/2014 3:12 PM

No connectors on this piece of coax.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 32883
Good Answers: 1795
#15

Re: Mystery Ohms

09/21/2014 1:59 PM

Sounds like you probably have a wire from the ground touching the center conductor....

Not hard to miss with old eyes....

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#16
In reply to #15

Re: Mystery Ohms

09/21/2014 3:06 PM

Checked and double checked...could this happen if water got into the cable?

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 32883
Good Answers: 1795
#20
In reply to #16

Re: Mystery Ohms

09/21/2014 4:59 PM

Yes, it could even happen if you happen to be touching the metal probes with your fingers....

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#21

Re: Mystery Ohms

09/21/2014 5:30 PM

Well I ordered a new digital unit that has pretty good reviews. Should have it in a few days.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#22
In reply to #21

Re: Mystery Ohms

09/21/2014 5:37 PM

Good for you. A man can't have too many tools.

Register to Reply
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#23

Re: Mystery Ohms

09/21/2014 6:05 PM

I would not put too much stock in the instrument, unless it has been calibrated.

Also, probes can sometimes be a fault issue.

If you really want to test the integrity of a transmission line you need a good RF test set, not a multi-meter.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#24
In reply to #23

Re: Mystery Ohms

09/21/2014 7:48 PM

Well the RF test set - or antenna analyzer will be here next weekend when we put my antenna back together. :-) I was just trying to get a quick sense of any shorts in the feed line. Now I've discovered I stated the problem azz backwards! must be the meds

I get a reading on the X1K scale not the X10 scale. I just went back into the ham shack and tested it again and the deflection is less than before, soooo...I think the line is probably OK, and the meter is suspect, but will prove it all out when we get the analyzer on the line!

This all started because my antenna (a 540ft horizontal loop) would not receive on any frequency. I suspected it had broken last winter when we had a lot of ice and one corner support gave way. What I found was the loop itself is still good with no breaks, but a connector, between the feed from the house and the fed to the antenna, had gotten water in and failed. The connector on the house side of that feed line looked good. So I started to check the feed line and here we are...now I 'll have a new digital meter, get my rig back on the air and enjoy life again!

73 - KG1O

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru

Join Date: Oct 2008
Posts: 42369
Good Answers: 1683
#25
In reply to #24

Re: Mystery Ohms

09/21/2014 8:08 PM

Wait a minute. Aren't Extra class operators supposed to know how to use these meter thingys.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#26
In reply to #25

Re: Mystery Ohms

09/21/2014 9:28 PM

I know how to use it...just didn't understand what I was seeing!

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
4
Guru
United States - Member - Born, raised halfway 'round .....

Join Date: May 2010
Location: Metro.Manila, Philippines.
Posts: 1211
Good Answers: 25
#27
In reply to #26

Re: Mystery Ohms

09/21/2014 10:26 PM

Try replacing the batteries inside your multimeter, they may be weak! Dead or weak batteries can give you intermittent ohmic readings! As indicated when change the range or sensitivity setting.

__________________
vsar
Register to Reply Good Answer (Score 4)
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#33
In reply to #24

Re: Mystery Ohms

09/22/2014 8:00 AM

Damn you!

I envy your loop!!!

I assume you are talking about a sky loop.

Instead of the 75Ω cable you would be far better off with ladder line and make it as much of the feed line as you can.

When I had mine the performance difference was very significant after replacing my coax with 300Ω ladder line.

You can even make your own ladder line, too.

Also, I would strip a foot or two off that coax at the end that feeds the loop and inspect the inside of the cable. If it looks stained it may have been compromised with water, which will kill your coax and give you an RF short.

Register to Reply Score 1 for Good Answer
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#34
In reply to #33

Re: Mystery Ohms

09/22/2014 8:54 AM

Yes it's a sky loop! It's up about 30ft in the trees near my house. The situation here does not allow for a ladder line, and the previous owner left 1000ft roll of RG6... so free coax and the need to run from the upper story of the house down to the basement, under the deck, and shed, and out 30ft to a tree, then up 30ft to a 1-1 balun...no way was I using ladder line! But when it's working I can tune from 10 to 160mhz just fine thank you! I've actually shortened it a bit to get the tuning right.

Maybe we can chew sometime.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru
United States - Member - Born, raised halfway 'round .....

Join Date: May 2010
Location: Metro.Manila, Philippines.
Posts: 1211
Good Answers: 25
#35
In reply to #34

Re: Mystery Ohms

09/22/2014 9:28 AM

When I was playing with that awhile back, I normally used an incandescent lamp to adjust and for peaking the actual / real transmitted power output... Tweaking my transmission line to achieve maximum light intensity out of say 500 or 1000 watt bulb. Lamp wattage normally depend on the power output capability of the final stage..

__________________
vsar
Register to Reply
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#37
In reply to #34

Re: Mystery Ohms

09/22/2014 10:28 AM

Best antenna I ever had. Mine was an 80 meter loop, but I loved the quiet performance and the higher the band, the better it performed. Worked a lot of QRP DX off of that antenna.

At the time I had a nice HP 8920A to help tune it, then I fine tuned the antenna with an old MFJ Versa Tuner II. I started with 75Ω feed line and no balun, but switched to the ladder line and the antenna really came alive.

Just recently reacquired another HP 8920B test set about a month ago, but sadly my property is not conducive to putting up another loop like that. Not sure what I will do yet.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#38
In reply to #37

Re: Mystery Ohms

09/22/2014 10:50 AM

This is my rig - Old Kenwood TS-830S, and yes the good old Versa tuner!

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#41
In reply to #38

Re: Mystery Ohms

09/22/2014 2:04 PM

I remember those! I serviced one or two long ago when I started a business for HAM radio repair. That is how I got my HP 8920A.

My first rig was a TS-530. Sold that to get a TS-440SAT, but that finally went belly up. I bought a TS-940 to replace it, but I really miss that 440.

Now that I have another HP 8920B RF test set I should be able to pull that old 440 out and get it working again. Just have to weed through my pile of junk to find the service manual. :-)

Register to Reply Off Topic (Score 5)
Guru

Join Date: Nov 2007
Location: Eastern Arizona mountains on Route 666 about a mile from God's country
Posts: 1676
Good Answers: 122
#42
In reply to #24

Re: Mystery Ohms

09/22/2014 3:21 PM

The analog meter when placed on the X1K scale applies a higher voltage to the test load which in this case is the coax cable and the meter movement is displaying the amount of current flowing in the circuit.

If you have a long antenna lead-in, the cable will mimic a capacitor and the initial ohmic reading will be high then as the cable (capacitor) charges the ohmic scale will deflect lower and lower.

Reversing the polarity of the meter leads after the cable charges will result in the same phenomonon but in the opposite polarity.

This can/will be magnified if you have a surge protector coupling in series with the lead-in.

__________________
They said; "Brain size?" I heard; "Train size?" so I said: "I'll take a small one, thank you."
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#44
In reply to #42

Re: Mystery Ohms

09/22/2014 6:38 PM

As I said elsewhere, "100ft of RG6 will only be about 1.6nF" - that is not going to give any noticeable effect with normal measuring tecniques at DC. Looking for a short with a DVM on any resistance scale is not going to be affected by 100ft of co-ax - all this talk of capacitance is bollocks.

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 31525
Good Answers: 833
#53
In reply to #44

Re: Mystery Ohms

12/10/2019 7:18 AM

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Nov 2012
Posts: 633
Good Answers: 13
#43
In reply to #24

Re: Mystery Ohms

09/22/2014 3:44 PM

Did you 'zero' it again when you changed scales?

Register to Reply
2
Power-User

Join Date: Dec 2013
Posts: 200
Good Answers: 5
#28

Re: Mystery Ohms

09/22/2014 4:01 AM

What could be happening is that when you check the resistance the first time you are charging the capacitor that the earth shield and centre wire makes. When you test the second time the charge flows through the meter and gives a false reading. Coax usually carries high frequency and this causes a capacitance so the 75 ohms is not pure resistance but impedance. Try the test again but short the outer shield and centre wire briefly before checking on the other range. Make sure that you do not as a source of resistance yourself, that is don't use your hands to hold the probes on the wires. Even cheap meters will do this well enough. Lets know how you get on

Register to Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#29
In reply to #28

Re: Mystery Ohms

09/22/2014 6:41 AM

Yes I'm now convinced I'm seeing capacitance. This line is long enough to do that and I have shorted the outer shield to the center, and do not touch any leads...I use shielded alligator clips.

So I'm seeing a discharging capacitor with a questionable meter...I will change the batteries this AM as well.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 467
#30
In reply to #28

Re: Mystery Ohms

09/22/2014 6:49 AM

100ft of RG6 will only be about 1.6nF between core and screen. A typical DMM (say, a Fluke 233) has an input resistance of about 10MΩ. That gives a time constant of about 16ms (if my envelope serves me well).

__________________
"Love justice, you who rule the world" - Dante Alighieri
Register to Reply Score 1 for Good Answer
Guru

Join Date: Apr 2012
Posts: 732
Good Answers: 17
#39
In reply to #28

Re: Mystery Ohms

09/22/2014 10:50 AM

Congrats and GA...you are the only one to mention that coaxial cable is measure in impedance, not resistance.

DC measurements of a piece of coax will not yield satisfactory results.

Coax can be measured in resistance per (1,000) foot.

OP: Try a step TDR for your measurements.

__________________
common knowledge...less common than common sense
Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#40
In reply to #39

Re: Mystery Ohms

09/22/2014 10:55 AM

I'm not trying to measure anything here. Just checking an antenna feed line to see if it's got a short, and happened upon this impedance reading. I'm convinced the line is good.

Thanks for the info.

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
2
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 646
#31

Re: Mystery Ohms

09/22/2014 7:29 AM

Mystery Ohms? Sounds like a job for Sherlock. You know, Sherlock Ohms.

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Register to Reply Good Answer (Score 2)
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#32
In reply to #31

Re: Mystery Ohms

09/22/2014 7:42 AM

Onto the naughty step- RIGHT NOW!

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru
Fans of Old Computers - ZX-81 - New Member

Join Date: Feb 2011
Location: 18N 65W o
Posts: 982
Good Answers: 27
#36

Re: Mystery Ohms

09/22/2014 10:25 AM

Some of the older meters had two batteries, 9 volt for higher ranges 1 1/2 for lower. The 1 1/2 may be defective. Can you "zero" the meter on the 1 ohm scale? The another possibility is the meter is accurate and you have faulty (the wire is corroded) connection. 500 ohms is a high unless it is exceptionally poor quality cable.

Register to Reply
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#45

Re: Mystery Ohms

09/22/2014 7:58 PM

OK - thanks for all the information here. It's been interesting to say the least!

I've replaced the connectors, sealed those that are exposed to the weather, and can tune the antenna again...even with one corner hanging about 4ft off the ground and a few branches hanging on the wire...it works!

So out of this adventure I got some new information, a new DVM in the mail, and a new battery powered soldering iron (just couldn't resist), and I'm back on the air!

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#46
In reply to #45

Re: Mystery Ohms

09/22/2014 11:16 PM

Great work!

I am glad to hear you are once more radioactive. ;-)

Register to Reply
Guru

Join Date: Nov 2012
Posts: 633
Good Answers: 13
#47

Re: Mystery Ohms

09/23/2014 9:13 AM

This thread makes me think I should add another project to my list...

#17 build ant. farm for my TS930s

Register to Reply Off Topic (Score 5)
Guru
Popular Science - Weaponology - New Member Fans of Old Computers - PDP 11 - New Member Technical Fields - Architecture - New Member Hobbies - HAM Radio - New Member

Join Date: Oct 2009
Location: Maine, USA
Posts: 2168
Good Answers: 71
#48
In reply to #47

Re: Mystery Ohms

09/25/2014 6:07 PM

This would be a good goal...

__________________
Tom - "Hoping my ship will come in before the dock rots!"
Register to Reply Off Topic (Score 5)
Guru
Popular Science - Evolution - New Member Popular Science - Weaponology - New Member

Join Date: May 2006
Location: The 'Space Coast', USA
Posts: 11109
Good Answers: 918
#49
In reply to #48

Re: Mystery Ohms

09/25/2014 8:49 PM

Not so much in Florida due to the threat of high hurricane winds.

Those are simply missiles waiting for ignition.

Register to Reply Off Topic (Score 5)
Register to Reply 53 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Anonymous Hero (6); Fredski (1); geraldpaxton (2); JE in Chicago (1); JohnDG (2); JWthetech (1); KeithMorin (2); lyn (7); prof peanut (1); PWSlack (1); RAMConsult (1); Rixter (1); SHOCKHISCAN (1); SimpleMind (1); SolarEagle (2); The.Tinkerer (1); Tom_Consulting (18); Tornado (1); Usbport (1); vsar (2)

Previous in Forum: Electrical Design for Large Building   Next in Forum: Connecting a Hooter with Output Contact of an Ammeter

Advertisement