Use of Hewlett packard 489a on DATV?

Help and support for the BATC DTX1 ATV digital encoder and modulator system
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g0uoz
Posts: 7
Joined: Fri Dec 28, 2012 11:57 pm

Use of Hewlett packard 489a on DATV?

Post by g0uoz » Mon May 05, 2014 5:08 pm

Use of Hewlett packard 489a on DATV?

Hi I am currently testing a Hewlett packard 489a on analogue ATV using a 13cm.co.uk tx 50mw with a lossy coax route to drop it for safety for the 489a.

I wonder if It will be suitable for running with a DX1 ?

Any further information on this amplifier would be appreciated, I have got the manual and currently getting about 4w output.... is this safe?

Advice/experiences would be wonderful.

Many thanks,

Tony - G0UOZ (mainly via GB3VL)

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am

Re: Use of Hewlett packard 489a on DATV?

Post by g4wvu » Tue May 06, 2014 9:11 am

Hi Tony, interesting way of upping a few miliwatts or so to a few watts.....TWT amplifier :) ! looks OK to me but I think 4w is probably pushing it hard. I expect a DTX1 will produce about 0.5w out when driving it directly (looking at the old spec sheet I found on line http://bee.mif.pg.gda.pl/ciasteczkowypotwor/HP/489A.pdf )

73s

mark

g0uoz
Posts: 7
Joined: Fri Dec 28, 2012 11:57 pm

Re: Use of Hewlett packard 489a on DATV?

Post by g0uoz » Tue May 06, 2014 10:16 am

HI Mark, yes I had never seen one and I am hoping its a bit like the old unit that was used in the early-est radar systems..

The manual says max input 100mw, but it trips out at the 50mw from the comtek unit,

quick calculation 1mw in = 1w out

so 100mw would = 10w .. obviously does not do this..

and.. 0.1mw (dtx1 : - 10dbm) = 1mw

I wonder if I am correct on this?

made me laugh at the huge size and voltage required to produce 1mw, but the unit is very interesting, looks like from a review it was made in the late 50's
and cost a staggering $700.

many thanks... Tony G0UOZ

g0uoz
Posts: 7
Joined: Fri Dec 28, 2012 11:57 pm

Re: Use of Hewlett packard 489a on DATV?

Post by g0uoz » Tue May 06, 2014 10:16 am

HI Mark, yes I had never seen one and I am hoping its a bit like the old unit that was used in the early-est radar systems..

The manual says max input 100mw, but it trips out at the 50mw from the comtek unit,

quick calculation 1mw in = 1w out

so 100mw would = 10w .. obviously does not do this..

and.. 0.1mw (dtx1 : - 10dbm) = 1mw

I wonder if I am correct on this?

made me laugh at the huge size and voltage required to produce 1mw, but the unit is very interesting, looks like from a review it was made in the late 50's
and cost a staggering $700.

many thanks... Tony G0UOZ

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am

Re: Use of Hewlett packard 489a on DATV?

Post by g4wvu » Tue May 06, 2014 12:28 pm

g0uoz wrote:and.. 0.1mw (dtx1 : - 10dbm) = 1mw

I wonder if I am correct on this?

made me laugh at the huge size and voltage required to produce 1mw, but the unit is very interesting, looks like from a review it was made in the late 50's
and cost a staggering $700.

many thanks... Tony G0UOZ
Yes I noticed the manual was 1970 :D . Standard DTX1 puts out about -4 , so +30 should give around 1/2 w (+26dBm ).
Out of interest I had a quick play with using a "Solent" tx as an amp for the DTX1 (to do a similar thing) .
I Increased the PA & drive biases to get better linearity & more gain to drive the usual M57762 23cm brick PA's. Works well - about 200mW from a standard DTX1 with good spectrum regrowth performance (-40 ish)........... which is great for driving the old bricks. Several locals were interested in re-using the FM kit they have where possible.
Just input-ed after the osc. & cut the DC to the osc. I might do a quick speel for CQTV etc. if any interest as there are hundreds of Solents about.

73s
Mark

g0uoz
Posts: 7
Joined: Fri Dec 28, 2012 11:57 pm

Re: Use of Hewlett packard 489a on DATV?

Post by g0uoz » Tue May 06, 2014 3:33 pm

MMM.. very interesting, i run a solent most of the time and a solent variant too... yes please put more details up..

Thanks for the power op etc for the dtx-1 ... my brain was starting to hurt.. :-)

I wonder if you went to the ATV / dtx-1 talk at finnigly, a wonderful weekend, I think the next one is bristol ? I will be going if ££'s allow.

As GB3VL will be digital out and a/d input, as soon as we raise the funds, I will need a DTX-1 ... I call my solent "poor mans analogue" as a joke.

Many thanks .. Tony.,

G0UOZ

g8gtz
Posts: 1152
Joined: Wed Apr 07, 2010 6:26 pm

Re: Use of Hewlett packard 489a on DATV?

Post by g8gtz » Wed May 07, 2014 9:27 am

Hi CAT14 will actually be in Basingstoke - see http://www.batc.org.uk/forum/viewtopic.php?f=89&t=3767 or the last CQ-TV

We've done a special deal with the local hotel at £65 and the local travel lodge still has rooms at £46 but I'm sure there's others to be had if you search around early ;-)

Noel

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