Philips
D2935
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This receiver uses digitally
synthesised tuning from 150kHz to 30MHz and FM Band II
The shortwave broadcast bands
can be selected by stepping through the complete list and specific
frequencies selected by using the numbered keys on the panel
but only 9 memories are provided which is far too few for this
type of set. A BFO is provided for SSB reception as well as a
manual RF gain control, essential for best SSB results. There
is no means of selecting bandwidth which is a shame although
frequency stability is good enough to use a single sideband technique
along with the tunable BFO to reduce adjacent channel interference.
Tuning rate is two speed governed by the spin speed of the tuning
knob.
Annoyingly, FM reception is
not stereo and the S-meter does not work for FM
The biggest drawback with the
set is the on-off switch. It is impossible to pack the set in
a suitcase without the on/off switch becoming operated. When
you take the set anywhere it is therefore essential to remove
the six "D" size batteries to avoid strange noises
from your luggage.
With digitally tuned sets one
can set the frequency directly to a short wave broadcast station
and, if skip is right, you'll hear it immediately. With shortwave
reception, radio signals bounce off the ionosphere and the ground
or sea. Depending on the height of the particular section of
the ionosphere affecting the frequency you are tuned to, you
will hear stations at different distances from you. The frequency
at which a section of the ionosphere affects the shortwave signal
depends on a number of factors. The main one of these is the
effect of the sun. The sun's radiation produces a number of reflective
mirrors high above the earth's surface. Some frequencies will
pass straight through some layers but others will reflect completely
and bounce down towards the earth. The resulting reflected signal
may travel skywards then bounce back off the ionosphere again.
This process may continue until a signal has travelled all the
way round the earth. Occasionally you can hear two or more signals
giving an echo effect when they have bounced around the earth
in different directions to both appear at your aerial. Because
one may take longer to reach you, you get the echo effect. |
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I wrote this page back
in 2001, and as I pen this, some 19 years ago, I took a picture
of my treasured D2935, now in a very sorry state. I also noticed
I hadn't mentioned the origin of my set. Many years ago I worked
for Plessey Defence Systems, and after 20 years based at the
Liverpool Exchange Works factory I was moved, more than slightly
unwillingly because we had not long before, moved to Swan Cottage,
the birthplace of Lady Hamilton (she wasn't born with that name
of course), a large detached cottage built in 1724. Anyway, a
move to Christchurch, the HQ of Plessey Defence Systems had been
instructed so we moved, all expenses paid, including a nice allowance
to buy a new house. Having been there about a year I was summoned
to my bosses office and informed that as I had been with Plessey
for 21 years I had been given a long service award. That came
as a big surprise as the Liverpool site had a £50 long
service award which matured after 25 years. To my surprise I
was told that I could have up to £500 but it was to be
spent at Harrods in London. A trip, by first class rail for my
wife and myself, was also provided, as was afternoon tea in their
café. Our third child who was around 9 months old in 1986
would travel free of charge so a baby sitter would not be needed.
Generally, Harrods long service
award purchases were very boring (usually including the words
"lead crystal" because recipients must have thought
it somehow "appropriate? My most expensive purchases were
a racing bicycle and a Philips D2935 radio. Hence my use of the
words "treasured D2935". It was NOT a car boot purchase!
Trawling through a Forum the
other day I spotted some words of advice including "auction"
so looked and to my surprise a new front panel is available from
a chap in Holland. This is now on the way and hopefully, once
stuck in place, will restore my treasured radio back to health.
Read on..
Below is the circuit diagram...
click it to see full size. |
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Below... the front nicely restored.
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In its AM mode the receiver
is a double superhet with a first IF of 2.3MHz and a second IF
of 468KHz. Either its ferrite rod or whip aerial can be selected
for any AM frequency (not just short waves) and it has continuous
tuning from 146KHz to 29.999MHz (with no gaps) which makes it
really useful for searching out interference sources. In FM mode,
although it has only a single loudspeaker, it provides proper
stereo into headphones.
Alas, this receiver has a design
weakness. The on/off switch, a tiny push button, top left, can
too readily be accidentally turned on. This results in flat batteries
and these being very expensive D-types is a real let down. |
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pending... |
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