[Amps] Re: 10dB and propagation

[R.Measures]

On Feb 9, 2005, at 10:50 AM, David Lisney wrote:

> I think this thread has some interesting twists without going into  
> witchcraft.
>
> The standard practice of using switched attenuators and a measuring  
> receiver is commonly used in various EMC measurements etc. However I  
> feel in this scenario it may possibly produce subtley different  
> results than predicted.
>
> In the instance where a 20dB attenuator is used in front of the  
> receiver ALL signals in the passband of the front end will be  
> attenuated, perhaps this alone allows the receiver front end and IF  
> stages to recover somewhat causing the signal under scrutiny to  
> apparently look stronger, ie to have been increased by more than 20dB.

The receiver and attenuator used for measurements on days when 20db  
gain was observed was the same as those used on days when the observed  
gain was 23db.

> Other possible errors could relate to the receiver/antenna mismatch, a  
> 50 ohm 20dB attenuator will only produce a 20dB loss when correctly  
> terminated.

The same antenna was used for all tests.

> In cases like my FT990 the internal auto atu is bypassed on receive,  
> perhaps an area that needs more thought, certainly I doubt the  
> receiver is exactly 50 ohms anyway.
>
>> From experience over the years measurements that appear too good to  
>> be true
>> often are. Sometimes small errors accumulate, a shame really, the  
>> dc-dc converter with 102% efficiency could have made me rich! 73 de  
>> David
>
>
>
> ----- Original Message ----- From: <amps-request at contesting.com>
> To: <amps at contesting.com>
> Sent: Sunday, February 06, 2005 11:48 PM
> Subject: Amps Digest, Vol 26, Issue 26
>
>
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>>
>> Today's Topics:
>>
>>   1. SELL: Power/SWR Bridge Component Package (w2cqm at juno.com)
>>   2. Alpha 87A Problem (TNeill1648 at aol.com)
>>   3. AL-811 AMP. (Ray)
>>   4. Re: AL-811 AMP. (carl seyersdahl)
>>   5. W7EME 144 mcs. 8877 problems (Jeremy Alexander)
>>   6. Re: W7EME 144 mcs. 8877 problems (jeff millar)
>>   7. Fusing the Plate winding (Jim Isbell, W5JAI)
>>   8. Re: 10dB and propagation (K3BU at aol.com)
>>   9. Re: 10dB and propagation (Ian White G3SEK)
>>  10. Re: QRO (John Irwin)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sun, 6 Feb 2005 12:19:48 -0500
>> From: w2cqm at juno.com
>> Subject: [Amps] SELL: Power/SWR Bridge Component Package
>> To: Amps at contesting.com
>> Message-ID: <20050206.122037.3880.0.W2CQM at juno.com>
>> Content-Type: text/plain; charset=us-ascii
>>
>> Offering a legal limit+, small footprint, relative power/SWR bridge  
>> pick
>> up component assembly. Can be series installed permanently in an
>> amplifier's output circuit or mounted outboard in a project box as a
>> custom, relative power/SWR bridge. Complete with the pickup assembly,
>> matched diodes, forward/reverse meter adjustment rheostats, and  all
>> wiring. Ready to drop in!  Includes the RF shield (amp mounting) and
>> hardware. Tested and operating perfectly. Removed intact from a Yaesu
>> amplifier. $20+ shipping Ron W2CQM/3
>>
>> http://swap.qth.com/453692.jpg
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Sun, 6 Feb 2005 14:29:50 EST
>> From: TNeill1648 at aol.com
>> Subject: [Amps] Alpha 87A Problem
>> To: amps at contesting.com
>> Message-ID: <2b.6c32ea64.2f37ca2e at aol.com>
>> Content-Type: text/plain; charset="US-ASCII"
>>
>> I am experiencing my first ever problem with my 87A.  The problems  
>> appears to
>> be the "ON" switch not functioning properly.
>>
>> The amp was working fine when I turned it off but failed to turn ON  
>> the next
>> day.  Fuses are OK and the amp is getting AC power.  The internal  
>> fuse by the
>> AC strip next to the rear panel is OK also.
>>
>> Wonder if anyone knows of a method of checking the "ON" switch without
>> removing the front panel or if you might know of something else to  
>> check.
>>
>> Thanks for the assistance.
>>
>> Tom K4XG
>>
>>
>> ------------------------------
>>
>> Message: 3
>> Date: Sun, 6 Feb 2005 14:46:55 -0500
>> From: "Ray" <w8cnl at mindspring.com>
>> Subject: [Amps] AL-811 AMP.
>> To: "AMPS" <amps at contesting.com>
>> Message-ID: <016a01c50c84$9d2940b0$d289bd3f at W8CNL>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> AL-811 AMP.
>> Three 572b's
>> AC on,  Opr off.
>> Tubes light up
>> HV shows about 1800 volts
>> Ip shows no grid current
>> Opr to XMIT
>> Nothing, no red xmit light, no standby grid current,can not key amp.
>> I don't believe the antenna change over relays are operating.
>> Turn off at night, was working great. Next morning nothing.
>>
>> Nice little amp when it works. Sucks when it doesn't.
>> Any ideas ?? What breaks by turning it off ( or on).
>> Any mods for this thing? Meter lights last about 4 or 5 months.
>> My 751A keys it perfect. First thing it did was burn relay contacts  
>> in my 761.
>>
>> * * * * * * * * * * * * * * * * * * * * * * * *
>> Raymond H. McClure - W8CNL
>> 5 McKenzie Circle
>> North Augusta, S.C.
>> 29841-4319
>>
>> Meddle not in the Affairs of Dragons, for Thou Art Crunchy and Taste  
>> Good with Catsup or BBQ Sauce
>>
>> * * * * * * * * * * * * * * * * * * * * * * * *
>>
>>
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Sun, 6 Feb 2005 16:07:32 -0500
>> From: "carl seyersdahl" <carlseye at tampabay.rr.com>
>> Subject: Re: [Amps] AL-811 AMP.
>> To: "Ray" <w8cnl at mindspring.com>
>> Cc: Amps at contesting.com
>> Message-ID: <00d901c50c8f$e3e4b380$f13bca44 at tampabay.rr.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Ray. It would seem that the op/stby switch has failed , because if  
>> that
>> switch doesn't work you wont get a transmit lite , and the antenna  
>> relay
>> can't operate either.It's also possible you've lost the gnd  
>> connection that
>> keys the amp . Also, you shouldnt have any grid current in stby  
>> anyway.
>> There is peculiarity in the metering which I've seen before, but  
>> that's
>> another story and has no bearing on the current problem.
>>    carl / kz5ca
>> ----- Original Message ----- From: "Ray" <w8cnl at mindspring.com>
>> To: "AMPS" <amps at contesting.com>
>> Sent: Sunday, February 06, 2005 2:46 PM
>> Subject: [Amps] AL-811 AMP.
>>
>>
>> AL-811 AMP.
>> Three 572b's
>> AC on,  Opr off.
>> Tubes light up
>> HV shows about 1800 volts
>> Ip shows no grid current
>> Opr to XMIT
>> Nothing, no red xmit light, no standby grid current,can not key amp.
>> I don't believe the antenna change over relays are operating.
>> Turn off at night, was working great. Next morning nothing.
>>
>> Nice little amp when it works. Sucks when it doesn't.
>> Any ideas ?? What breaks by turning it off ( or on).
>> Any mods for this thing? Meter lights last about 4 or 5 months.
>> My 751A keys it perfect. First thing it did was burn relay contacts  
>> in my
>> 761.
>>
>> * * * * * * * * * * * * * * * * * * * * * * * *
>> Raymond H. McClure - W8CNL
>> 5 McKenzie Circle
>> North Augusta, S.C.
>> 29841-4319
>>
>> Meddle not in the Affairs of Dragons, for Thou Art Crunchy and Taste  
>> Good
>> with Catsup or BBQ Sauce
>>
>> * * * * * * * * * * * * * * * * * * * * * * * *
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 5
>> Date: Sun, 6 Feb 2005 13:23:24 -0800
>> From: "Jeremy Alexander" <oaxaca at oregoncoast.com>
>> Subject: [Amps] W7EME 144 mcs. 8877 problems
>> To: <amps at contesting.com>
>> Message-ID: <LNEILDCCGNGGJDLMNLLGOEHACMAA.oaxaca at oregoncoast.com>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Aloha to all:
>>
>> My QRO is having fits. I have an 8877 on 144 Mcs, the classic w6po  
>> design.
>> It is showing some arcing at the control grid ring to chassis ground.  
>> This
>> should be a low-inductance coupling shouldn't it? Instead of a  
>> continuous
>> finger stock, it has four, three fingered pieces at each 90 degrees  
>> around
>> the grid ring. Arcing is occurring between the fingers and grid ring.  
>> Were
>> the fingers attach to the chassis, things look clean. I assume this  
>> "less
>> than great" (my opinion) configuration is to allow more airflow  
>> through the
>> chimney aperture? I think I can hear faint arcing sounds inside the  
>> cabinet
>> causing these small pitting in the grid ring.
>>
>> Also about the same time my input tuning is not consistent. I use an
>> external input tuning network, two series inductances and a shunt  
>> capacitor.
>> I sometimes need to retune the cap to get coupling with the QRO?
>>
>> I see all of this as a changing input impedance due to the changing  
>> grid to
>> ground resistance???
>>
>> Have any of you encountered these symptoms before? I am getting a lot  
>> of
>> mail back saying this ground to grid arrangement is not suitable at  
>> 144
>> mcs., however people seem to still be building these the same way!?  
>> It looks
>> too easy to simply finger all the way around the grid ring and  
>> pressurize
>> the cabinet in a more appropriate matter, with chimney on top of the  
>> valve?
>> OR, Is my tube tired again already? Is it shorted between the control  
>> grid
>> and cathode, only under load somehow? Or, another problem?
>>
>> Any help is welcome.
>>
>> 73 Jeremy
>> http://www.oregoncoast.com/oaxaca
>>
>>
>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 6
>> Date: Sun, 06 Feb 2005 17:03:19 -0500
>> From: jeff millar <wa1hco at adelphia.net>
>> Subject: Re: [Amps] W7EME 144 mcs. 8877 problems
>> To: Jeremy Alexander <oaxaca at oregoncoast.com>
>> Cc: amps at contesting.com
>> Message-ID: <42069427.10406 at adelphia.net>
>> Content-Type: text/plain; charset=iso-8859-1; format=flowed
>>
>> Jeremy...
>>
>> I've seen this behavior with light output loading, which causes the Q  
>> of
>> the output network to soar and results in very high circulating
>> currents.  All the plate network circulating current flow through the
>> grid ring.  The high currents then burn the contact points between the
>> finger stock and the grid ring.  Once the contact points begin to
>> overheat, it snowballs into serious problems.
>>
>> The solution is to replace the fingers, polish the grid ring, ensure  
>> the
>> finger pressure is high, use as many fingers as possible and always  
>> tune
>> up from the more heavily loaded side of the operation...or use very
>> light drive while hunting for the correct operating point.
>>
>> jeff, wa1hco
>>
>> Jeremy Alexander wrote:
>>
>>> Aloha to all:
>>>
>>> My QRO is having fits. I have an 8877 on 144 Mcs, the classic w6po  
>>> design.
>>> It is showing some arcing at the control grid ring to chassis  
>>> ground. This
>>> should be a low-inductance coupling shouldn't it? Instead of a  
>>> continuous
>>> finger stock, it has four, three fingered pieces at each 90 degrees  
>>> around
>>> the grid ring. Arcing is occurring between the fingers and grid  
>>> ring. Were
>>> the fingers attach to the chassis, things look clean. I assume this  
>>> "less
>>> than great" (my opinion) configuration is to allow more airflow  
>>> through the
>>> chimney aperture? I think I can hear faint arcing sounds inside the  
>>> cabinet
>>> causing these small pitting in the grid ring.
>>>
>>> Also about the same time my input tuning is not consistent. I use an
>>> external input tuning network, two series inductances and a shunt  
>>> capacitor.
>>> I sometimes need to retune the cap to get coupling with the QRO?
>>>
>>> I see all of this as a changing input impedance due to the changing  
>>> grid to
>>> ground resistance???
>>>
>>> Have any of you encountered these symptoms before? I am getting a  
>>> lot of
>>> mail back saying this ground to grid arrangement is not suitable at  
>>> 144
>>> mcs., however people seem to still be building these the same way!?  
>>> It looks
>>> too easy to simply finger all the way around the grid ring and  
>>> pressurize
>>> the cabinet in a more appropriate matter, with chimney on top of the  
>>> valve?
>>> OR, Is my tube tired again already? Is it shorted between the  
>>> control grid
>>> and cathode, only under load somehow? Or, another problem?
>>>
>>> Any help is welcome.
>>>
>>> 73 Jeremy
>>> http://www.oregoncoast.com/oaxaca
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>>
>>
>>
>>
>> ------------------------------
>>
>> Message: 7
>> Date: Sun, 6 Feb 2005 16:56:02 -0600
>> From: "Jim Isbell, W5JAI" <jim.isbell at gmail.com>
>> Subject: [Amps] Fusing the Plate winding
>> To: Mail List for Amplifiers <amps at contesting.com>
>> Message-ID: <b0295dbe0502061456278060a6 at mail.gmail.com>
>> Content-Type: text/plain; charset=US-ASCII
>>
>> I am in the final steps of designing and building a linear to
>> supplement my station om 160 thru 10 Meters.  The chassis is being
>> built at this time and I will soon be mounting parts.
>>
>> It is a single 4-1000A running GG with a plate supply that is
>> switchable in steps from 3KV to 6KV.  The transformer is a 12KVA
>> transformer which will obviously be able to handle 2 amps on the
>> secondary winding.  I will be using a pair of VT-42A Mercury vapor
>> rectifiers.
>>
>> Yes, I know there are "better" ways of doing it, but none would be
>> prettier.  This is to be an amp capable of full amateur legal limit
>> that will be a JOY TO WATCH. not just an appliance.
>>
>> OK, the questions.
>>
>> I have heard from very good authority that the mercury vapor
>> rectifiers might short on occasion and that the secondary of my plate
>> transformer would probably "fuse" just as fast (or even faster) as a
>> FB 1 amp fuse in the plate lead.
>>
>> The first question.  If I don't need a fuse any bigger than 1/2 amp
>> and the secondary is rated for 2 amps.  Will I be safe from blowing
>> the transformer?
>>
>> The second question.  If the above answer is NO, is there any circuit
>> I can build that will protect the transformer?
>>
>> I would sure hate to leave off the glow of a pair of VT-42As to light
>> the inside of the chassis around my 4-1000A which will be behind a
>> window.  This is art now, not engineering, and I sure like that purple
>> glow.
>>
>> --  
>> Jim Isbell
>> W5JAI
>> UltraVan #257
>> CAL - 27   #221
>>
>>
>> ------------------------------
>>
>> Message: 8
>> Date: Sun, 6 Feb 2005 18:08:32 EST
>> From: K3BU at aol.com
>> Subject: Re: [Amps] 10dB and propagation
>> To: amps at contesting.com
>> Message-ID: <a9.6c9306e8.2f37fd70 at aol.com>
>> Content-Type: text/plain; charset="US-ASCII"
>>
>> In a message dated 2/6/2005 9:57:54 AM Eastern Standard Time,
>> k7fm at teleport.com writes:
>>>> I used to wonder how come I could use a tri-band beam, advertised  
>>>> at 8 db
>> gain, and an amplifier advertised at 1500 watts and yet be 15 db down  
>> from
>> other local stations who were using 3 element mono-banders.  Since  
>> the power
>> limit is 1500 watts, they would naturally have been running the same  
>> power
>> as me.
>>
>> This non-linear ionospheric amplification must therefore have been the
>> explanation.  I had been puzzled for years.  They obviously lived in  
>> such a
>> duct, while I did not.<<
>>
>> You guys might try to poke fun at this. But there are many factors
>> contributing to signal levels received at the other end. Antenna  
>> pattern, local ground
>> conditions, terrain and propagation conditions.  VHFers know about  
>> ducting on
>> VHF between W6 and KH6, you drive up the hill and you can find spot  
>> where your
>> signal (few watts) will hit it and you QSO with KH6. You go few  
>> hundred feet
>> up or down and you lose it.
>>
>> Skewed and varying (high) angle propagation with spotlight effect is  
>> now
>> "normal" on 160m, where earlier when I mentioned it, I was "kockoo".
>>
>> Yuri, K3BU.us
>>
>>
>> ------------------------------
>>
>> Message: 9
>> Date: Sun, 6 Feb 2005 23:30:46 +0000
>> From: Ian White G3SEK <G3SEK at ifwtech.co.uk>
>> Subject: Re: [Amps] 10dB and propagation
>> To: amps at contesting.com
>> Message-ID: <syDlV9lmiqBCFAsb at ifwtech.co.uk>
>> Content-Type: text/plain;charset=us-ascii;format=flowed
>>
>> Yuri wrote:
>>> You guys might try to poke fun at this. But there are many factors
>>> contributing to signal levels received at the other end. Antenna
>>> pattern, local ground conditions, terrain and propagation conditions.
>>> VHFers know about ducting on VHF between W6 and KH6, you drive up the
>>> hill and you can find spot where your signal (few watts) will hit it
>>> and you QSO with KH6. You go few hundred feet up or down and you  
>>> lose it.
>>>
>> Sure, all of that is true... but it all goes strictly dB for dB. There
>> is no support for tropo ducts behaving in a non-linear fashion.
>>
>> Let's not confuse the variable *importance* of a dB under different
>> circumstances (which is obviously true) with any suggestion that the
>> propagation medium itself is non-linear.
>>
>> A non-linear medium would have to mean that your signal was directly
>> affecting the ionization density or the refractive index of the
>> troposphere. As I already said, that's wishful thinking at amateur  
>> power
>> levels.
>>
>>
>> --  
>> 73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
>> http://www.ifwtech.co.uk/g3sek
>>
>>
>> ------------------------------
>>
>> Message: 10
>> Date: Sun, 6 Feb 2005 15:48:21 -0800 (PST)
>> From: John Irwin <crazytvjohn at yahoo.com>
>> Subject: Re: [Amps] QRO
>> To: PA3DUV <pa3duv at planet.nl>
>> Cc: amps at contesting.com
>> Message-ID: <20050206234821.92851.qmail at web21006.mail.yahoo.com>
>> Content-Type: text/plain; charset=us-ascii
>>
>> LACK OF MONEY  CAN BE A STRONG MODIVATOR
>>
>> JOHN KB9TC
>>
>>
>> PA3DUV <pa3duv at planet.nl> wrote:
>> Yes, thats right, Ray has been selling on e-bay but he has stopped  
>> about 6
>> months ago. I'm surprised to see him him back.
>>
>> Cheers, Dick
>> PA3DUV
>>
>> ----- Original Message ----- From: "Will Matney"
>> To:
>> Sent: Sunday, February 06, 2005 5:23 AM
>> Subject: Re: [Amps] QRO
>>
>>
>>> Heh, just shows how much I pay attention, not much! I seen he has a
>>> feedback of only 9 and figured he's only been on there for a short  
>>> time.
>>> That's the first one I'd ever seen on there of his. That's not very  
>>> many
>>> over a 3 year period. I just looked and he's be there since 2002.
>>> Evidently, he just dont sell much on there.
>>>
>>> Will
>>>
>>>
>>> On Sat, 5 Feb 2005 23:18:33 -0500, Pat Poirier wrote:
>>>
>>>> Will,
>>>>
>>>> Ray has been selling his amplifiers on eBay for quite some time  
>>>> now. I
>>>> was surprised to see them there for the first time about a year ago.
>>>>
>>>> 73,
>>>> Pat W1KA
>>>>
>>>> ----- Original Message ----- From: "Will Matney"
>>>> To:
>>>> Sent: Saturday, February 05, 2005 10:41 PM
>>>> Subject: [Amps] QRO
>>>>
>>>>
>>>>> Anybody ever notice that QRO Tech. was selling now on eBay?
>>>>>
>>>>> http://cgi.ebay.com/ws/eBayISAPI.dll? 
>>>>> ViewItem&category=48700&item=5749412310&rd=1
>>>>>
>>>>>
>>>>> Will
>>>>>
>>>>> -- Using Opera's revolutionary e-mail client:  
>>>>> http://www.opera.com/mail/
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps at contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>>
>>>>
>>>>
>>>>
>>>> __________ NOD32 1.880 (20040928) Information __________
>>>>
>>>> This message was checked by NOD32 antivirus system.
>>>> http://www.nod32.com
>>>>
>>>>
>>>
>>>
>>>
>>> -- 
>>> Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>
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>> ------------------------------
>>
>> _______________________________________________
>> Amps mailing list
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>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>> End of Amps Digest, Vol 26, Issue 26
>> ************************************
> _______________________________________________
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org