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HOME » ANTENY NA PASMA MIKROFALOWE » OFFSET DISH VS. PRIME FOCUS DISH...

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Offset dish vs. prime focus dish...

...dyskusja...
  
SP2RXX
23.11.2016 16:37:59
poziom najwyższy i najjaśniejszy :-)



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Lokalizacja: Bydgoszcz JO83XC

Posty: 6864 #2362453
Od: 2011-6-25


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Ciekawa dyskusja...warto sie zapoznac...

Dnia Wtorek, 22 Listopada 2016 20:57 <dl7yc@snafu.de> napisał(a)
> Just another comment regarding the discussion offset dish vs. prime focus
> dish:
>
>
> Both "sides" claim better results, but reality shows the truth, hi.
>
> If you calculate the "shadow" of the feed-system (in my perspective
> including the WG-switch, preamp, transverter AND TWT with power supply for
> 10 GHz OR 24GHz) its 1-2% of the whole surface only !! (based on my 2.4 m
> precision prime focus dish)
>
> The results for such a setup showing moon- and sunnoise results very close
> as predicted in VK3UM`s programs. Compared with other well equiped stations
> nothing is worse, therefore the effiency should be as high as caculated.
> And...... the feed design and focal point adjustment / calculation is VERY
> easy.
>
> Looking to my friends having offset dishes the same size, its all a bit
> motre complicated. I know all the recommendations from Hannes well and they
> where all very helpful. Even the "trick" with the waterhose, I think Dick,
> PA2DW told this, is very nice and helps a lot....
>
> But the offset feed design and adjustment to its phase center is much, much
> more complicated than it looks. I personally know some very wellknown
> Microwave EME friends, struggeling many times to "optimize" their dish
> performance.
>
> If one loose 5% effiency due to a "bad" phase center, not perfect adapted
> feed in respect to the dish`s f/D (i.e. wrong feed system selection) and
> therefore spillover results in AZ or EL orientation due to "breaking"
> the -10dB rule in one direction at least, this all together is MORE worse,
> than a 2% "feedbox"-shadow of a prime focus RX/TX setup with no extra line
> losses !! Its true ... , especially for the more rectangular beam of the
> Super-VE4MA-Feed (Kumar feed / see W1GHZ handbook).
>
> Therefore, it could be allready an open question!! If one have a PERFECT
> offeset dish setup, this might be 2% better compared to the same prime focus
> dish setup ?? But if NOT, hmm....
>
> My reccommendation:
>
> Try to put the equipment you need for the given band straight inline with
> the prime focus feedhorn and beat your neighbour with more moonnoise
> performance, hi. Forget struggeling and time consuming processes to optimize
> overall performance of microwave EME dishes.
> But, .... you really will loose the possibility to SIT on the ground for
> adjustment of your offset feed, because NO adjustment is neccessary
> anymore!! And the focalpoint of an 2.4m prime focus dish is 1.2 m far from
> the surface only (plus some extra cm) Feed change is not a dangerous thing !
>
> I NEVER re-adjusted the feedsystems in its focal point after a perfect
> calculation and mechanical measurement by a laser distance meter from a
> hardware shop.
>
> BUT at the end: its much more important to be QRV than to grab the last
> tenth of a dB !!!!!!!!!!!!!!!
>
> Vy 73 Manfred, DL7YC
>
>
> 2.4m precision prime focus dish (Areal OY Finnland), f/D 0.4 used for 10 GHz
> and 24 GHz
> VE4MA "Super feeds" for both QRG`s
> 0.6dB NF (10GHz) 1.3dB NF (24 GHz)
> DB6NT transverter with 10 MHz time base connection (GPS)
> modified RW1127 TWTA`s with RWN 320 PSU`s
> Output: > 90 watts (10GHz) 40 watts (24 GHz)
> Autotracking NITEC rotator
>
>
> -----Ursprüngliche Nachricht-----
> From: moon-net-request@mailman.pe1itr.com
> Sent: Tuesday, November 22, 2016 8:37 AM
> To: moon-net@mailman.pe1itr.com
> Subject: Moon-net Digest, Vol 289, Issue 16
>
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> than "Re: Contents of Moon-net digest..."
>
>
> Today's Topics:
>
> 1. Icom 9100 and RigBlaster Advantage (Richard Lawn)
> 2. Re: FLEX 1500 & MAP65 (Edward R Cole)
> 3. Re: 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM FOR 1296
> (Edward R Cole)
> 4. Re: 3cx1500 or 3cpx1500 (Mark)
> 5. Re: 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM FOR 1296
> (Hansen Peter)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 21 Nov 2016 18:24:12 -0500
> From: Richard Lawn <rjlawn@gmail.com>
> Subject: [Moon-Net] Icom 9100 and RigBlaster Advantage
> To: moon-net@mailman.pe1itr.com
> Message-ID:
> <CADQmrTGeLWopjcimwxCyaPX7fvKXcT5BchQc=_LnuQ-nZCjf_w@mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> I took someone's advice and added the RigBlaster Advantage to my new EME
> station. Now I'm getting sufficient audio in to WSJT and beginning to
> decode some signals. Next step is activating PTT to the DEMI sequencer
> which works great and PTT on the radio seems to work but I'm not getting
> any audio in to the radio. I've fiddled and fiddled with the Icom menu but
> to no avail. Someone out there must be using the 9100 with an external
> sound card and I'd love to hear from you.
>
> 73
> Rick, W2JAZ
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> ------------------------------
>
> Message: 2
> Date: Mon, 21 Nov 2016 14:28:05 -0900
> From: Edward R Cole <kl7uw@acsalaska.net>
> Subject: Re: [Moon-Net] FLEX 1500 & MAP65
> To: Cowles Andrus III K4EME <candrus@mgwnet.com>, Moon-net
> <moon-net@mailman.pe1itr.com>
> Message-ID: <201611212327.uALNRoje010308@mail42c28.carrierzone.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Cowles,
>
> I didn't reply on the Flex-1500 but have heard that quite a few who
> bought them for eme or mw IF use with transverters had sold the Flex
> citing freq instability and interfacing issues.
>
> I waited several years, using a FT-847 on 2m and on 1296 with144/1296
> transverter. But having heard such glowing comments on the K3 for
> CW use, I decided using transverters with top-end HF radio made for a
> superior eme and VHF-mw operation. I bought my K3 in 2010 and
> commissioned DEMI to build a custom dual-Rx transverter to use with
> MAP65 for adaptive-pol receiving (IQ+ was not available at that time).
>
> Since have acquired the 220, 432, 1296 transverters using 28-MHz as
> std IF. I am not upgrading to the K3S as most of the upgraded boards
> are available to install in my K3 (I bought the new synth boards
> which I have not yet installed). I decided to buy the K3/10 which
> does not have the 100w HF amp inside the radio. I also have a KX3 so
> bought the separate KXPA-100 for use on HF/6m by either radio. Cost
> is about the same.
>
> The K3S is expensive but ranks at the top of the list compared with
> other HF radios and very popular with dxpeditions due to
> size/weight. I think their transverter I/F is superb in comparison
> with other makers. No computer I/F is required -
> plug-n-play. Transverter output is 0.1-1.5mw so take that into
> consideration for obtaining compatible transverters. Rx and Tx
> separate connectors std. And great Tx-inhibit function makes
> sequencing fool-proof.
>
> Guess you would say I like my K3.
>
> But saying that the KX3 is pretty nice and is usable with
> transverters with a little more work in doing the I/F.
>
> 73, Ed - KL7UW
>
> At 09:35 AM 11/21/2016, Cowles Andrus III K4EME wrote:
>
> >I want to thank VE4MA, W2HRO, KC4SW and everyone else who responded
> >to my email about using the FLEX 1500 with MAP 65.
> >
> >It appears at this time no one has been able to get theses two to
> >play together, so I don't plan to buy the FLEX 1500.
> >
> >Some have recommended the Elecraft K3S!
> >
> >The K3S would cost considerable more than the FLEX 1500, so I may
> >put the K3S on my wish list!
> >
> >Thank you & 73!
> >
> >Cowles K4EME
> >Home page: <http://cowlesradio.webs.com/>http://cowlesradio.webs.com/
> >_______________________________________________
> >Moon-Net posting and subscription instructions are at
> >http://www.nlsa.com/nets/moon-net-help.html
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> "Kits made by KL7UW"
> Dubus Mag Business e-mail:
> dubususa@gmail.com
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> ------------------------------
>
> Message: 3
> Date: Mon, 21 Nov 2016 14:54:38 -0900
> From: Edward R Cole <kl7uw@acsalaska.net>
> Subject: Re: [Moon-Net] 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM
> FOR 1296
> To: serge <ve1kg@eastlink.ca>, moon-net@mailman.pe1itr.com
> Message-ID: <201611212356.uALNuGoa023083@mail40c28.carrierzone.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Serge,
>
> Just my opinion but if you can acquire an offset feed dish I suggest
> its slightly better:
> 1. Feed does not block part of the dish surface (no apparent shadow)
> 2. It requires a narrower beamwidth feed that may improve rejection
> of ground noise pickup (lower sidelobes; better G/T)
> 3. You can mount all the electronics at the feed eliminating
> feedline losses (max bang for the buck)
> 4. Often these dish surface are rated to 10-12 GHz so multi-band use
> is greater.
>
> The feed support would need to be robust to handle the higher weight
> at the feed.
> Dish may be fiberglass vs mesh so heavier weight.
> Cost may be higher
>
> Az-El requirements are the same.
>
> Offset dish needs a feed designed for a F/d of 0.6-0.7 (W2IMU would
> work). Ordinary septum would not be good.
> I believe VE4MA is using one on 24/47 GHz so ask him about feedhorns.
>
> I have a idle 1.8m offset feed dish I am considering for 10-GHz
> use. It used to be our satellite-TV dish until recently switching to
> Direct-TV (which included free dish and HD receiver). Recently
> occurred to me that 6-foot (1.8m) makes it a candidate for portable
> use with our RV trailer.
> http://www.kl7uw.com/1.8m_dish.jpg
>
> 73, Ed - KL7UW
>
> At 12:00 PM 11/21/2016, serge wrote:
> >Which is best a 2.4M prime focus dish or a 2.4M offset dish? & WHY?
> >What kind of septum would you use on both dishes for 1296???
> >Thank you
> >Serge, VE1KG
> >_______________________________________________
> >Moon-Net posting and subscription instructions are at
> >http://www.nlsa.com/nets/moon-net-help.html
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> "Kits made by KL7UW"
> Dubus Mag Business e-mail:
> dubususa@gmail.com
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>
> ------------------------------
>
> Message: 4
> Date: Tue, 22 Nov 2016 00:23:04 +0000
> From: Mark <EA8FF@yahoo.com>
> Subject: Re: [Moon-Net] 3cx1500 or 3cpx1500
> To: moon-net@mailman.pe1itr.com
> Message-ID: <3e5c9c39-211b-84e7-d078-7d83d4999470@yahoo.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Hi,
>
> 3cx1500 and 3cpx1500 are the same tubes, they were probably selected
> after production on flashover voltage and stamped differently. the
> 3cpx1500 were more expensive than the 3cx1500. Nowadays new design uses
> LDMOS and most people think the 3cpx1500 is only for pulse, thats why
> there less expensive. Same thing with 3cx800 and 3cpx800.
>
> 73, Mark EA8FF
>
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 22 Nov 2016 07:36:40 +0000
> From: Hansen Peter <peter.hansen@dk.saabgroup.com>
> Subject: Re: [Moon-Net] 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM
> FOR 1296
> To: Edward R Cole <kl7uw@acsalaska.net>, serge <ve1kg@eastlink.ca>,
> "moon-net@mailman.pe1itr.com" <moon-net@mailman.pe1itr.com>
> Message-ID:
> <8d659953b4264132b3a5212f53301d4f@corpappl841.corp.saab.se>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi All I am an extensive user of a Offset dishes.
> I started out with a 1.8meter offset dish (6foot) with 35W in the feed. I
> worked easily 35initials on CW and it would have been going on. But 1? year
> ago I changed to a 2.4meter Offset dish and this really opened the world. I
> use the dish on 3 and 6cm currently but will do 24Ghz also. My dish is
> channel master/Andrew dish. The mesh is small enough for use on 24Ghz.
> I can confirm most of the things KL7UW states. The dish is easy to feed
> linear on 3cm as there are waveguide feeds used originally that works great.
> On 6cm where I am circular I designed my own feed type as I find W2IMU feed
> little off peak being used for my dish. I had 0.2dB too little Moonnoise on
> 6cm. I know I could have tried with larger W2IMU feeds but I went another
> way.
> Efficiency is much better on the Offset dish due to low blockage and higher
> efficiency in the Feed to illuminate a higher F/d.
>
> What can be worked on a 2.4meter ??
> 3CM
> I worked a 90cm that was using 12W in JT4F EME
> I worked a 90cm that was using 25W in CW
>
> 6CM
> I worked a 1meter and 10W in CW
>
> Many qso is possible just try it out.
>
> All forgot one VERY NICE feature on Offset dish. When I work on my Feeds,
> Change system etc I simply sit on the ground and have the feed just in front
> of me. Or I can tilt the dish and work on it standing up.
>
>
> 73 Peter OZ1LPR
>
> From: moon-net-bounces@mailman.pe1itr.com
> [mailto:moon-net-bounces@mailman.pe1itr.com] On Behalf Of Edward R Cole
> Sent: 22. november 2016 00:55
> To: serge; moon-net@mailman.pe1itr.com
> Subject: Re: [Moon-Net] 2.4M PRIME FOCUS / 2.4M OFFSET/ ALSO SEPTUM FOR 1296
>
> Serge,
>
> Just my opinion but if you can acquire an offset feed dish I suggest its
> slightly better:
> 1. Feed does not block part of the dish surface (no apparent shadow)
> 2. It requires a narrower beamwidth feed that may improve rejection of
> ground noise pickup (lower sidelobes; better G/T)
> 3. You can mount all the electronics at the feed eliminating feedline
> losses (max bang for the buck)
> 4. Often these dish surface are rated to 10-12 GHz so multi-band use is
> greater.
>
> The feed support would need to be robust to handle the higher weight at the
> feed.
> Dish may be fiberglass vs mesh so heavier weight.
> Cost may be higher
>
> Az-El requirements are the same.
>
> Offset dish needs a feed designed for a F/d of 0.6-0.7 (W2IMU would work).
> Ordinary septum would not be good.
> I believe VE4MA is using one on 24/47 GHz so ask him about feedhorns.
>
> I have a idle 1.8m offset feed dish I am considering for 10-GHz use. It
> used to be our satellite-TV dish until recently switching to Direct-TV
> (which included free dish and HD receiver). Recently occurred to me that
> 6-foot (1.8m) makes it a candidate for portable use with our RV trailer.
> http://www.kl7uw.com/1.8m_dish.jpg
>
> 73, Ed - KL7UW
>
> At 12:00 PM 11/21/2016, serge wrote:
>
> Which is best a 2.4M prime focus dish or a 2.4M offset dish? & WHY? What
> kind of septum would you use on both dishes for 1296???
> Thank you
> Serge, VE1KG
> _______________________________________________
> Moon-Net posting and subscription instructions are at
> http://www.nlsa.com/nets/moon-net-help.html
>
> 73, Ed - KL7UW
> http://www.kl7uw.com
> <http://www.kl7uw.com/> "Kits made by KL7UW"
> Dubus Mag Business e-mail:
> dubususa@gmail.com<mailto:dubususa@gmail.com>
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> ------------------------------
>
> _______________________________________________
> Moon-Net posting and subscription instructions are at
> http://www.nlsa.com/nets/moon-net-help.html
>
> End of Moon-net Digest, Vol 289, Issue 16
> *****************************************
>
> _______________________________________________
> Moon-Net posting and subscription instructions are at http://www.nlsa.com/nets/moon-net-help.html




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