Wanted: NEC UHF TV amp pallet


Andrew
 

Hi,
I understand they are all spoken for but if one becomes available I'd be very interested.
Thanks,
Andrew
G4XZL


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


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


eightyelectric
 

Marek

You got a lower counter offer than I did. Mine was £500!!

I would certainly be interested in at least 2 boards please.

Paul G6UAJ 


On Wed, 14 Sep 2022 at 9:25, 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


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


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:

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



Dave G8KHU
 

Hi Neil

If still available I'd like the £125 unit and promise to sell on then remaining pallets :)

Dave G8KHU


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 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


Steve G4HTZ
 

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 


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


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 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.

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.


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


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.

--
Mike G0MJW


--
Robin Szemeti - G1YFG


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
Sent: 16 September 2022 15:57
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Wanted: NEC UHF TV amp pallet

 

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.

--
Mike G0MJW


--
Robin Szemeti - G1YFG


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:

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
Sent: 16 September 2022 15:57
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Wanted: NEC UHF TV amp pallet

 

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.

--
Mike G0MJW


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Steve G4HTZ
 

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 


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


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.
--
Mike G0MJW


--
Robin Szemeti - G1YFG


David GM6BIG
 

Hi all,

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:

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.

--
Mike G0MJW

--
Robin Szemeti - G1YFG