[TowerTalk] Measuring Coax Loss

Thu Feb 11 17:32:51 PST 2010

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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>>>
>>>
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