Wanted: NEC UHF TV amp pallet
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Andrew
Hi,
I understand they are all spoken for but if one becomes available I'd be very interested. Thanks, Andrew G4XZL
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Gareth G4XAT
If you are stuck, there is a seller on eBay (wildly optimistic!!) who has taken offers IRO £300 for a unit. https://www.ebay.co.uk/itm/185566977308
Given he probably paid between £20 and £125 for them and possibly bought 'unseen' thinking they might be audio amps (looking at what else he is selling) you might get lucky. You will get 2 Docherty boards on big copper spreaders, 4 standard boards on smaller copper spreaders and 8 plain old bolt-down but otherwise identical boards, all of which deliver the goods. 300W CW before any compression. Each. :-) Good luck. Gareth
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Marek Szuba
As I am interested in 2-3 of these boards myself I've made an offer of 300 pounds on this auction (thanks, Gareth!), and the seller has just responded with a counter-offer of 400. Before I proceed, could I possibly get a quick show of hands regarding who might want these boards afterwards? I'll sell them at cost, or possibly even slightly below that because I want to keep the casing. -- Marek M0JUR
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eightyelectric
Marek
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You got a lower counter offer than I did. Mine was £500!! I would certainly be interested in at least 2 boards please.
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a a
Marek also interested in one please.. Alec G8GON On Wednesday, 14 September 2022, 09:25:38 BST, Marek Szuba via groups.io <marek.szuba@...> wrote: As I am interested in 2-3 of these boards myself I've made an offer of 300 pounds on this auction (thanks, Gareth!), and the seller has just responded with a counter-offer of 400. Before I proceed, could I possibly get a quick show of hands regarding who might want these boards afterwards? I'll sell them at cost, or possibly even slightly below that because I want to keep the casing. --Marek M0JUR
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Neil Smith G4DBN
Folks, those prices are more than a bit
of a ripoff. If someone will do the donkey work of dismantling
(looking at you Marek!), I have one spare unit left which could be
collected from here or I could ship it at cost. First £125
secures, but I need a firm promise that it will be dismantled and
pallets sold on to others at a fair cost. Sorry I don't have time
to do the work myself right now.
I still have a couple that are promised
to others, and one more unit that I'll sell on for £100 if someone
will remove one PSU and one of the Dohertys and post those back to
me.
All are new, unused and dated 2017.
UH-101X model.
On 14/09/2022 10:14, a a via groups.io
wrote:
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Dave G8KHU
Hi Neil
If still available I'd like the £125 unit and promise to sell on then remaining pallets :) Dave G8KHU
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Marek Szuba
On 2022-09-14 11:12, Neil Smith G4DBN wrote:
Folks, those prices are more than a bit of a ripoff. If someone will do theGiven that Dave has already requested the 125-GBP unit, I'll take care of the ship-back 100-pound one for you. Incidentally, in case it helps avoid shipping - looks like I will be at the National Hamfest, and will definitely attend the RSGB Convention. -- Marek M0JUR
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I just bought a unit for a offer of £350 ….hopefully something to play with after I move qth
-- Steve G4HTZ JO01JN60 Great Wakering, Essex 24ghz 1.8w 80cm dish also known to be active occasionally on 70cms DATV
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Mike Willis
What are you doing with the PSU Neil? I have one sitting in the garage. I couldn't see how we could re-use them, at least not easily.
-- Mike G0MJW
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Neil Smith G4DBN
Hi Marek, it's yours. I'm tied up with
work and visitors. so will get a price when I have a minute and
email you direct.
Ta, Neil
On 14/09/2022 12:04, Marek Szuba via
groups.io wrote:
On 2022-09-14 11:12, Neil Smith G4DBN wrote:Folks, those prices are more than a bit of a ripoff. If someone will do the donkey work of dismantling (looking at you Marek!), I have one spare unit left which could be collected from here or I could ship it at cost. First £125 secures, but I need a firm promise that it will be dismantled and pallets sold on to others at a fair cost. Sorry I don't have time to do the work myself right now. I still have a couple that are promised to others, and one more unit that I'll sell on for £100 if someone will remove one PSU and one of the Dohertys and post those back to me. All are new, unused and dated 2017. UH-101X model.Given that Dave has already requested the 125-GBP unit, I'll take care of the ship-back 100-pound one for you. Incidentally, in case it helps avoid shipping - looks like I will be at the National Hamfest, and will definitely attend the RSGB Convention. -- Marek M0JUR
--
Neil G4DBN
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Neil Smith G4DBN
I want to chop one up and see if I could do *something* with it, perhaps just fitting a new switchmode controller/driver and use the power devices/transformers and the caps and rectifiers, but as you say, it's not easy without knowledge of the controller and connections. I thought it might be worth spending a couple of hours hacking, to see if there are possible mods like those on some of the blade rack SMPS units. I have plenty of other PSUs though, so it would really just be a thing to put on Youtube if there is a suitable hack. It would be neat to have one of the units with four PAs and a combiner and PSU, just ticking over, and run that down in the old pighouse 120m from the house, feeding a decent antenna array, cooled with a strong antifreeze solution.
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Neil G4DBN
On 15/09/2022 12:38, Mike Willis wrote:
What are you doing with the PSU Neil? I have one sitting in the garage. I couldn't see how we could re-use them, at least not easily.
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Mike Willis
Will you be able to afford the electricity? One thing I would like to find out if possible is what voltage did it run at. I see no difference in (sensible) power output down to 40V. Efficiency seems higher at lower voltages so I wonder if these pallets were intended to operate at 50V or were designed for a lower voltage for better reliability.
-- Mike G0MJW
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Robin Szemeti - G1YFG
Efficiency may improve at lower voltages, but I bet the IMD goes up significantly.
On Fri, 16 Sept 2022 at 11:49, Mike Willis <willis.mj@...> wrote: Will you be able to afford the electricity? One thing I would like to find out if possible is what voltage did it run at. I see no difference in (sensible) power output down to 40V. Efficiency seems higher at lower voltages so I wonder if these pallets were intended to operate at 50V or were designed for a lower voltage for better reliability. --
Robin Szemeti - G1YFG
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Conrad, PA5Y
The last 2 paragraphs in Mike’s NEC PA pallet. pdf suggest otherwise, perhaps you did not see it as you were travelling.
73
Conrad PA5Y
From: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
On Behalf Of Robin Szemeti - G1YFG via groups.io
Efficiency may improve at lower voltages, but I bet the IMD goes up significantly.
On Fri, 16 Sept 2022 at 11:49, Mike Willis <willis.mj@...> wrote:
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Robin Szemeti - G1YFG
I've not seen and PDF's ... on a carrier/FM type signal I would expect the efficiency to improve as the voltage was lowered without affecting 3rd harmonic too badly ... however I would expect IMD on SSB signals to worsen .. if you have a copy of the PDF, id be interested to see any SSB measurements versus voltage.
On Fri, 16 Sept 2022 at 15:11, Conrad, PA5Y <g0ruz@...> wrote:
--
Robin Szemeti - G1YFG
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My pallet just arrived from the eBay seller via parcelforce 24 …bigger and heavy than I thought..like trying to carry a AR88 down the garden .
not sure what’s inside …I have already got a single board from Gareth …but time is limited due to a up and coming house move , so will be a while before I open the beast up . Steve G4HTZ JO01JN60 Great Wakering, Essex 24ghz 1.8w 80cm dish also known to be active occasionally on 70cms DATV
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Mike Willis
I was looking for a new document and then realised! It doesn't seem to have a bad effect of DVB-S or DVB-T but maybe SSB would suffer, not sure. Given the tendency for many 12V 'Linears' to be run near saturation, they will probably still be cleaner.
-- Mike G0MJW
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Robin Szemeti - G1YFG
I can certainly see an improvement in IMD when running my small[1] 144MHz LDMOS linear at 65V over 48V ... sadly the PSU I ended up using won't quite make the full 65V, but it gets close.
On Fri, 16 Sept 2022 at 16:53, Mike Willis <willis.mj@...> wrote: I was looking for a new document and then realised! It doesn't seem to have a bad effect of DVB-S or DVB-T but maybe SSB would suffer, not sure. Given the tendency for many 12V 'Linears' to be run near saturation, they will probably still be cleaner. --
Robin Szemeti - G1YFG
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David GM6BIG
Hi all,
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Robin is right, IMD suffers. Akin to splatter in SSB. The two-tone linearity test shows up IMD for SSB. COFDM has many "tones". Often called spectral growth. That growth is inside the COFDM too, and interferes with the wanted carriers. The COFDM requires very linear amplification to minimise the intermodulation between the carriers. We have many versions and makes of the pallets in service at work. But they all work in more or less the same way. In Digital TV service they are probably not running at the full pallet output, governed by the ERP required from antenna(s). Voltages/Currents adjusted for efficiency dependant on power and freqy. (Several pallets/bays combined as required). So, in short, they are run a little inside IMD (& MER) performance specification to get best efficiency. Voltage is AOT --- Adjust On Test Cheers, David On 16/09/2022 14:57, Robin Szemeti -
G1YFG via groups.io wrote:
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