[TowerTalk] Measuring Coax Loss

Thu Feb 11 17:42:05 PST 2010

But let's put it in perspective.  

Suppose you're putting up a new antenna system and have two 100' lengths of
coax to choose from, one of which has 1dB more loss than the other.  

How much is that 1dB worth to you?  10 cents/foot?  20?  50?   Suppose you
have to make the same choice for 4 or 5 runs of the same coax.  Where do you
draw the line?

I certainly get your point... I think the question is, where is the point of
diminishing returns?

I have a different perspective.  Aside from my time when I was a kid, I
never had a 'decent' antenna system.  I moved every couple of years for the
24 of the past 29 years.  I used low wires and whatever else I could put up.
I have confirmed over 200 countries and never applied for DXCC because it's
not important to me.  

How much would I pay for that extra dB?  Not a cent.  

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Dan Schaaf
Sent: Thursday, February 11, 2010 8:33 PM
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] Measuring Coax Loss

I spend most of my waking hours working DX.  And since I have worked 308 
countries on most bands, I hunt for those that I have not yet worked on 
certain bands. Tonite for example I worked DU9 on 15 meters SSB. Koichi was 
just above the noise except for some QSB when he dropped in/out. Most of 
what I need is weak. I did the  308 countries during the last 5 years when 
the SSN was in decline.

Best Regards
Dan Schaaf
K3ZXL   www.k3zxl.com   "In the Beginning, there was Spark Gap"
===============================
NOBSKA
www.nobska.net
===============================
Cape Cod Instruments
www.oceanbiz.net
===============================
----- Original Message ----- 
From: "Mike Besemer (WM4B)" <mwbesemer at cox.net>
To: "'Tower and HF antenna construction topics.'" <towertalk at contesting.com>
Sent: Thursday, February 11, 2010 8:26 PM
Subject: Re: [TowerTalk] Measuring Coax Loss

> How, it the real world of ham radio, do you experience hearing the
> difference of 3dB daily?
>
> I'm not talking about a lab.
>
>
>
> -----Original Message-----
> From: towertalk-bounces at contesting.com
> [mailto:towertalk-bounces at contesting.com] On Behalf Of Dan Schaaf
> Sent: Thursday, February 11, 2010 8:24 PM
> To: Tower and HF antenna construction topics.
> Subject: Re: [TowerTalk] Measuring Coax Loss
>
> I am not " thinking what I want". I know this to be fact.
> I experience it daily.
> Nobody is disqualifying you or accusing you of stupidity. There is a
> difference between stupidity and ignorance. Ignorance is "not knowing or 
> not
>
> having been educated". Stupidity is knowing and still being defiant of the
> knowledge.
> You come to this and other groups for knowledge.
>
>
> Best Regards
> Dan Schaaf
> K3ZXL   www.k3zxl.com   "In the Beginning, there was Spark Gap"
> ===============================
> NOBSKA
> www.nobska.net
> ===============================
> Cape Cod Instruments
> www.oceanbiz.net
> ===============================
> ----- Original Message ----- 
> From: "Mike Besemer (WM4B)" <mwbesemer at cox.net>
> To: "'Tower and HF antenna construction topics.'" 
> <towertalk at contesting.com>
> Sent: Thursday, February 11, 2010 8:13 PM
> Subject: Re: [TowerTalk] Measuring Coax Loss
>
>
>> Think what you want, Dan... I stand by my argument that 99% of the time
>> 3dB
>> is inaudible.
>>
>> I love the sanctimonious attitude on this list.  If somebody disagrees,
>> they're automatically unqualified or stupid.
>>
>> That's why I left last time.
>>
>>
>> -----Original Message-----
>> From: towertalk-bounces at contesting.com
>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Dan Schaaf
>> Sent: Thursday, February 11, 2010 8:07 PM
>> To: Tower and HF antenna construction topics.
>> Subject: Re: [TowerTalk] Measuring Coax Loss
>>
>> A really serious DXer is concerned about these losses.
>> Someone who casually operates may not care too much.
>> The  point is that all losses add up.
>> I CAN hear the difference.
>> For example.  +/- 3 db is either 1/2 or 2 x the power whether transmitted
>> or
>>
>> received. I can clearly hear the difference in a weak signal if  itdrops3
>> db
>>
>> or raises 3 db.
>> I think that you are just repeating something that you heard and have not
>> actually experienced these differences on the  air.
>>
>>
>> Best Regards
>> Dan Schaaf
>> K3ZXL   www.k3zxl.com   "In the Beginning, there was Spark Gap"
>> ===============================
>> NOBSKA
>> www.nobska.net
>> ===============================
>> Cape Cod Instruments
>> www.oceanbiz.net
>> ===============================
>> ----- Original Message ----- 
>> From: "Mike Besemer (WM4B)" <mwbesemer at cox.net>
>> To: "'Tower and HF antenna construction topics.'"
>> <towertalk at contesting.com>
>> Sent: Thursday, February 11, 2010 8:01 PM
>> Subject: Re: [TowerTalk] Measuring Coax Loss
>>
>>
>>>I qualified my comments to exclude microwave/weak signal work.
>>>
>>> If you have that many connectors in-line, how concerned are you REALLY
>>> about
>>> loss?
>>>
>>> C'mon guys... for HF and probably VHF, it isn't that critical.
>>>
>>> WM4B
>>>
>>> -----Original Message-----
>>> From: towertalk-bounces at contesting.com
>>> [mailto:towertalk-bounces at contesting.com] On Behalf Of Dan Schaaf
>>> Sent: Thursday, February 11, 2010 7:45 PM
>>> To: Tower and HF antenna construction topics.
>>> Subject: Re: [TowerTalk] Measuring Coax Loss
>>>
>>> Having been a calibration Engineer in my early days, I concur with Jim.
>>> In addition, each coax connector inline introduces losses. They all add
>>> up.
>>> Definitely worse in VHF/UHF. Some folks say you can't hear the
>>> difference,
>>> but when you are trying to hear and work a weak signal in/above the
>>> noise,
>>> every db counts.
>>>
>>> Dan Schaaf
>>> K3ZXL
>>> "In the Beginning there was Spark Gap"
>>> www.k3zxl.com
>>> ----- Original Message ----- 
>>> From: "Jim Brown" <jim at audiosystemsgroup.com>
>>> To: "Tower and HF antenna construction topics."
>>> <towertalk at contesting.com>
>>> Sent: Thursday, February 11, 2010 7:34 PM
>>> Subject: Re: [TowerTalk] Measuring Coax Loss
>>>
>>>
>>>> On Thu, 11 Feb 2010 19:03:51 -0500, Mike Besemer \(WM4B\) wrote:
>>>>
>>>>>Still... a dB or so (or even 3) on a long run of coax isn't going to
>>>>> make a  hill of beans difference for most applications... an S-Unit
>>>>>is ~ 6dB.
>>>>
>>>> Only by someone's definition, not in reality. If you actually MEASURE
>>>> the
>>>> response of the S-meters in REAL radios, you find that an S-unit may be
>>>> close
>>>> to 6dB near S9, but is usually closer to 3dB at S5 and below.
>>>>
>>>> As to a hill of beans -- many hams have long runs of coax to their
>>>> antennas,
>>>> so loss can be a BIG deal, not a hill of beans. The loss in dB of
>>>> verious
>>>> RG8
>>>> style coaxes ranges by a factor of about 2:1 from the lowest to the
>>>> highest.
>>>> Over the past several years, I've been doing a lot of little things to
>>>> improve my station. A dB here, a dB there, they all add up. Smart
>>>> operators
>>>> know that. The difference between a 3-el yagi and a 4-el yagi of
>>>> comparable
>>>> design is only 1-2 dB, and often double the cost. That doesn't stop a
>>>> lot
>>>> of
>>>> guys who have the space from putting up 4-el yagis!
>>>>
>>>> Somehow, the scientific method seems to be lost on some of those
>>>> commenting
>>>> on my post. How do you know that the MFJ (or any piece of test gear) is
>>>> accurate if you don't compare it to another measurement or test method
>>>> of
>>>> known accuracy? I'll bet a six pack of your favorite 807s that if I had
>>>> posted loss measuerements made ONLY with an MFJ, someone would have
>>>> pooh-
>>>> poohed them because I didn't use equipment traceable to a calibration
>>>> lab.
>>>>
>>>>>Forgot to mention... unless I actually SAW the 10' piece being cut off
>>>>>the
>>>>>longer roll I was considering buying from, I wouldn't trust the
>>>>>measurements
>>>>>anyway.
>>>>
>>>> Did it ever occur to you that sometimes ham stores, even the best 
>>>> known,
>>>> with
>>>> the biggest ads in QST, may not have good data on what they're selling?
>>>> I
>>>> don't trust some of them any more than an anonymous vendor in a flea
>>>> market.
>>>> But there ARE some good deals out there, IF you have an open mind and
>>>> know
>>>> how to evaluate them. The point of my post was to show that you CAN get
>>>> decent data from an MFJ259B that has been calibrated if you're 
>>>> measuring
>>>> a
>>>> sample that is long enough.
>>>>
>>>> How many measurements of coax loas have you actually made? How did you
>>>> do
>>>> it?
>>>> How did you know that you had good data? At some point, you've got to
>>>> know
>>>> exactly how long that piece of coax is. RG8 is big and heavy, so
>>>> unspooling
>>>> enough of it to get a good measurement isn't always easy. You've got to
>>>> deal
>>>> with the length of cable sample you can get.
>>>>
>>>> 73,
>>>>
>>>> Jim K9YC
>>>>
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
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>>>> TowerTalk at contesting.com
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>>>
>>>
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