Was my father's homebrew double conversion SW receiver a HBR?
 

On Mar 20, 6:47*pm, ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:
The design used plug-in coils for the osc and rf stages, and
*they were double conversion designs, with a first IF of
*1600 kc and a second IF of either 100 kc or 85 kc (when
*using surplus ARC-5 IFTs.) *The 1800 mc xtal you bought
*your dad was used for the second coversion osc. to convert
*the 1600 kc IF down to 100 kc. *Many hams deviated from
*the exact original IF frequencies (i.e. strong local BC
*station on 1600 kc) which might explain why the xtal

was chosen for 1800 kc instead of 1500 or 1700.
We have a local mid power station at 1600KHz, WWRL, at my parents' house,
so my father might have wanted to avoid problems with it.

His radio had a bandswitch instead of plug in coils, and he'd receive
various broadcast SW stations. *He wasn't a ham at the time just yet.. *

I had a friend who was a retired engineer with GE turned TV tech who
built
one with a band switch and he later modified it to
be more of a general purpose SW receiver. His name was Olin Griggs.

Jimmie.

I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. *The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. *I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. * Maybe they could be cleaned up, but it no longer
seems worth the effort. *My new idea is to use miniature relays to
switch the circuits. *I recently found nearly a gross of small relays
for free so why not?- Hide quoted text -

- Show quoted text -

I tried the TV tuner trick one time and it didnt work well at all.
Most tuners are tossed because the contacts fail. Various contact
cleaners will only help for a while because wor out is worn out and
there is not a long term fix you can do for them. The exception to
this was a very old one I found that was at least as big or bigger
than a shoe box. Shame on me but I used one like this to build my own
CB radio tx. I was using it to switch crystals and trimmer caps for
the osc.


Jimmie

Was my father's homebrew double conversion SW receiver a HBR?
 

JIMMIE wrote:
On Mar 20, 6:47 pm, ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:
The design used plug-in coils for the osc and rf stages, and
they were double conversion designs, with a first IF of
1600 kc and a second IF of either 100 kc or 85 kc (when
using surplus ARC-5 IFTs.) The 1800 mc xtal you bought
your dad was used for the second coversion osc. to convert
the 1600 kc IF down to 100 kc. Many hams deviated from
the exact original IF frequencies (i.e. strong local BC
station on 1600 kc) which might explain why the xtal
was chosen for 1800 kc instead of 1500 or 1700.
We have a local mid power station at 1600KHz, WWRL, at my parents' house,
so my father might have wanted to avoid problems with it.
His radio had a bandswitch instead of plug in coils, and he'd receive
various broadcast SW stations. He wasn't a ham at the time just yet.
I had a friend who was a retired engineer with GE turned TV tech who
built
one with a band switch and he later modified it to
be more of a general purpose SW receiver. His name was Olin Griggs.
Jimmie.
I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. Maybe they could be cleaned up, but it no longer
seems worth the effort. My new idea is to use miniature relays to
switch the circuits. I recently found nearly a gross of small relays
for free so why not?- Hide quoted text -

- Show quoted text -

I tried the TV tuner trick one time and it didnt work well at all.
Most tuners are tossed because the contacts fail. ...


Not really. Back then TVs were often tossed because the flyback xfmr had
blown and repair was deemed uneconomical. Or someone said that because
in reality they wanted that brand spanking new set that was one sale.

But this is so long ago that if there's any left the contacts will have
corrodes away.

[...]

--
73, Joerg

Was my father's homebrew double conversion SW receiver a HBR?
 

"Joerg" posted on Fri, Mar 20 2009 6:06 pm

ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:

I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. Maybe they could be cleaned up, but it no longer
seems worth the effort. My new idea is to use miniature relays to
switch the circuits. I recently found nearly a gross of small relays
for free so why not?

Relays will most likely bring some grief over the years with contacts
not conducting 100% and such. Better use band switching diodes or PIN
diodes.

I disagree based on some experience in environmentally testing relays
ranging from high-power to low-power to 'choppers' in so-called
stabilized
(DC) amplifiers for military avionics, then doing comparative testing
against the cheaper commercial relay designs on the market over 50
years
ago.

About the only "grief" is one can get is failure to wire it correctly
or
not understanding what relay contacts acually do or how to power their
actuating coils.

Power relays CAN result in contact pitting and poor resistance as a
result
of many multiple activations while carrying inductive loads of many
Amperes of current with resulting very high voltage back-EMF
('flyback')
conditions on contact separation. That is NOT the case with receiver
bandswitching applications. Not even close.

There are some unusual contact effects in so-called "dry" circuits
carrying femtoAmpere currents or less but those won't affect high-
impedance input and output circuits common to vacuum tubes. One of
the
better choices for no-nonsense, easier to implement bandswitch
conversions without much cost is to use modern, easy-to-get small
relays
requiring only 100 to 150 mW coil powers, available in coil operating
voltage increments of 6, 12, 18, 24 VDC...or, if salvaging older tube
equipment, the "plate relays" of a half century ago designed for
higher
12 to 30 VDC, comparable powers for a few mA of plate current in
coils.
[much harder to get now given all electronics is firmly in the solid-
state era starting over 40 years ago] Some relay makers, such as
Omron, are widely used in electronics, especially for automotive
applications and are found listed in all major distributor catalogs.

Relay contacts can easily withstand 200 to 400 VDC stock of now v. old
(half-century ago). The make or break contacts do NOT involve any
unusual RF impedance characteristics other than a few pFd of
capacitance
equivalent to ordinary point-to-point wiring or the lead-length
inductance of some short point-to-point wire inductance in the low
nanoHy range. It has an excellent open or closed contact condition
with excellent isolation between actuating coil and contact set.

By contrast, conventional rotary bandswitch structures designed around
60 to 70 years ago, are open to all sorts of contamination, including
OXIDATION of contacts plus wear of typically cheap contact
construction
of a bygone era. Sealed or semi-sealed rotary switch wafers of the
post-WWII era have much longer life than the old open-to-everything
wafer designs that may look good in their first half decade, then
degrade from oxidation after that, before normal wear effects show up.

Based on over a decade of using the TV channel "turret tuner" (such as
the cheap products of Standard Coil tuners of long ago) types just for
TV channel selection, I wouldn't try to convert those to anything else
than scrap. I'm being kind on that evaluation. The MECHANICS of such
turret tuners may look good, but VHF-UHF circuits don't work on either
mechanics or appearance. HF circuits might squeak by, but the typical
contact set of turret tuners was never optimized for either wear or
contact resistance. It was 'optimized' entirely for maximum profit
from
lowest-possible cost of components in a highly-competitive TV market
of
long ago.

Today there are a number of inexpensive small relays used in HF radio
equipment, especially in automatic antenna tuners (used for switching
banks of binary-progression-values of inductors and capacitors) from
direct microcontroller control of actuating coils. Those work very
well
and show no degredation running with 100 W of RF or more at 50 Ohm
impedances. Millions of automobiles on the road today are tooling
around
with little packages of relays controlling everything from headlights
to
sensor selection in adverse temperature ranges and high vibration, no
real problems from those relays.

In short, small semi-sealed low-power relays are FINE for vacuum tube
circuit switching in homebrew electronics, properly applied. They can
easily replace most rotary bandswitching applications in layout with
less stray circuit series-inductance and parallel-to-ground
capacitance
than with point-to-point wiring.

73, Len AF6AY

Was my fatehr's homebrew double conversion SW receiver a HBR?
 

On Mar 17, 10:12�pm, Robert casey wrote:
Looking thru a friend's Feb 2009 QST, saw an article on the W6TC "HBR"
double conversion homebrew radio. �Which my father may have built a copy
of. �I no longer have that radio, but looking at the pictures of teh sets
in the QST article, it looks very similar to what my father built. �I do
remember that he used a 1.8MHz crystal for what might have been the 1st IF
to 2nd IF conversion mixer. �I also remember, in the mid 60's (I was in
grammar school) getting this crystal for my father as an Xmas gift (well, I
gave him money that he used to order the crystal, I would not have been old
enough to know how to mail order stuff myself yet). �

Anyway, did the HBR use a crystal of a frequency like this as a conversion
local osc mixer? �Or maybe the crystal wasn't in an oscillator circuit, but
maybe as a bandpass filter? �

Bob, try www.qsl.net/k5bcq/HBR/hbr.html for a rather complete
collection of
Home Brew Receiver photos, schematics, details, hints&kinks, etc.,
which is Kees Talen's website. It isn't as squashed together as QST
articles (which don't cover all the HBR versions) nor does it have the
extra 450 KB warning page present with QST article downloads.

73, Len AF6AY

Was my father's homebrew double conversion SW receiver a HBR?
 

AF6AY wrote:
"Joerg" posted on Fri, Mar 20 2009 6:06 pm

ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:

I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. Maybe they could be cleaned up, but it no longer
seems worth the effort. My new idea is to use miniature relays to
switch the circuits. I recently found nearly a gross of small relays
for free so why not?
Relays will most likely bring some grief over the years with contacts
not conducting 100% and such. Better use band switching diodes or PIN
diodes.

I disagree based on some experience in environmentally testing relays
ranging from high-power to low-power to 'choppers' in so-called
stabilized
(DC) amplifiers for military avionics, then doing comparative testing
against the cheaper commercial relay designs on the market over 50
years
ago.

About the only "grief" is one can get is failure to wire it correctly
or
not understanding what relay contacts acually do or how to power their
actuating coils.

Power relays CAN result in contact pitting and poor resistance as a
result
of many multiple activations while carrying inductive loads of many
Amperes of current with resulting very high voltage back-EMF
('flyback')
conditions on contact separation. That is NOT the case with receiver
bandswitching applications. Not even close.

There are some unusual contact effects in so-called "dry" circuits
carrying femtoAmpere currents or less but those won't affect high-
impedance input and output circuits common to vacuum tubes. One of
the
better choices for no-nonsense, easier to implement bandswitch
conversions without much cost is to use modern, easy-to-get small
relays
requiring only 100 to 150 mW coil powers, available in coil operating
voltage increments of 6, 12, 18, 24 VDC...or, if salvaging older tube
equipment, the "plate relays" of a half century ago designed for
higher
12 to 30 VDC, comparable powers for a few mA of plate current in
coils.
[much harder to get now given all electronics is firmly in the solid-
state era starting over 40 years ago] Some relay makers, such as
Omron, are widely used in electronics, especially for automotive
applications and are found listed in all major distributor catalogs.

Relay contacts can easily withstand 200 to 400 VDC stock of now v. old
(half-century ago). The make or break contacts do NOT involve any
unusual RF impedance characteristics other than a few pFd of
capacitance
equivalent to ordinary point-to-point wiring or the lead-length
inductance of some short point-to-point wire inductance in the low
nanoHy range. It has an excellent open or closed contact condition
with excellent isolation between actuating coil and contact set.

By contrast, conventional rotary bandswitch structures designed around
60 to 70 years ago, are open to all sorts of contamination, including
OXIDATION of contacts plus wear of typically cheap contact
construction
of a bygone era. Sealed or semi-sealed rotary switch wafers of the
post-WWII era have much longer life than the old open-to-everything
wafer designs that may look good in their first half decade, then
degrade from oxidation after that, before normal wear effects show up.

Based on over a decade of using the TV channel "turret tuner" (such as
the cheap products of Standard Coil tuners of long ago) types just for
TV channel selection, I wouldn't try to convert those to anything else
than scrap. I'm being kind on that evaluation. The MECHANICS of such
turret tuners may look good, but VHF-UHF circuits don't work on either
mechanics or appearance. HF circuits might squeak by, but the typical
contact set of turret tuners was never optimized for either wear or
contact resistance. It was 'optimized' entirely for maximum profit
from
lowest-possible cost of components in a highly-competitive TV market
of
long ago.

Today there are a number of inexpensive small relays used in HF radio
equipment, especially in automatic antenna tuners (used for switching
banks of binary-progression-values of inductors and capacitors) from
direct microcontroller control of actuating coils. Those work very
well
and show no degredation running with 100 W of RF or more at 50 Ohm
impedances. Millions of automobiles on the road today are tooling
around
with little packages of relays controlling everything from headlights
to
sensor selection in adverse temperature ranges and high vibration, no
real problems from those relays.

In short, small semi-sealed low-power relays are FINE for vacuum tube
circuit switching in homebrew electronics, properly applied. They can
easily replace most rotary bandswitching applications in layout with
less stray circuit series-inductance and parallel-to-ground
capacitance
than with point-to-point wiring.


Relays are ok in those applications, where there are actual currents
flowing. What I meant was pure signal switching with no DC currents.
Sealed relays, Reeds, mercury-wetted and such work quite well there. But
non-sealed versions have issues and a snap-on plastic cap ain't a seal.
Those problems became really nasty after we moved across an ocean and
all this stuff was in a sea container for two months. After that almost
all the band switching relays had problems, had to clean all of them.
Now I am down to one sticky relay every couple month or so. Some I have
replaced with PIN diode circuits and that, of course, made the issues
completely go away. But it's always a hassle to do in an exisitng circuit.

--
73, Joerg

Was my father's homebrew double conversion SW receiver a HBR?
 

"Joerg" wrote in message
Yeah, I wish the designers of the NRD-515 here had known that as well.
Every few months a relay will become "sticky". The S-meter drops to zilch,
rock the attenuator switch 5-10 times, and it's back :-(

Relays with some current are ok but I prefer the electronic method. PIN
diodes with lots of current and plenty of carrier lifetime usually work.
One just has to make sure there aren't any rectification effects that can
cause IM or harmonics in the presence of strong signals. FET switches are
sometimes a good deal as well but since the SD5000 and SD5400 have gone
towards high-priced boutique status not so much anymore.

--
73, Joerg

Hello Joerg

Odd you're having that problem with the NRD-515. So far mine
has been rock solid, except for the rotting foam disease in the
mechanical filters... But... I do have constant problems with
the relay that selects the external VFO in the NSD-515
transmitter! It always needs attention and cleaning. Its the
odd-ball relay that was added on the bottom of the mother
board. I'm wondering if you have had the same problem
with the transmitter (assuming you own the pair) and what
you did to fix it.

73

Peter k1zjh

Was my father's homebrew double conversion SW receiver a HBR?
 

Unca Pete wrote:
"Joerg" wrote in message
Yeah, I wish the designers of the NRD-515 here had known that as well.
Every few months a relay will become "sticky". The S-meter drops to zilch,
rock the attenuator switch 5-10 times, and it's back :-(

Relays with some current are ok but I prefer the electronic method. PIN
diodes with lots of current and plenty of carrier lifetime usually work.
One just has to make sure there aren't any rectification effects that can
cause IM or harmonics in the presence of strong signals. FET switches are
sometimes a good deal as well but since the SD5000 and SD5400 have gone
towards high-priced boutique status not so much anymore.

--
73, Joerg

Hello Joerg

Odd you're having that problem with the NRD-515. So far mine
has been rock solid, except for the rotting foam disease in the
mechanical filters... But... I do have constant problems with
the relay that selects the external VFO in the NSD-515
transmitter! It always needs attention and cleaning. Its the
odd-ball relay that was added on the bottom of the mother
board. I'm wondering if you have had the same problem
with the transmitter (assuming you own the pair) and what
you did to fix it.


Actually I only have the receiver. Besides relays there is one other
serious problem: The bearings of the tune encoder are seriously worn,
the shaft sloshes around. I am not looking forward to the day when I
have to disect that thing.

Rotting foam in filters? Whoops, I've got to watch out for that. As for
relays, my problem really got worse after all this was in a sea
container for a while and crossed an ocean.

--
73, Joerg

Was my father's homebrew double conversion SW receiver a HBR?
 

On Mar 21, 5:11*pm, Joerg
wrote:
JIMMIE wrote:
On Mar 20, 6:47 pm, ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:
The design used plug-in coils for the osc and rf stages, and
*they were double conversion designs, with a first IF of
*1600 kc and a second IF of either 100 kc or 85 kc (when
*using surplus ARC-5 IFTs.) *The 1800 mc xtal you bought
*your dad was used for the second coversion osc. to convert
*the 1600 kc IF down to 100 kc. *Many hams deviated from
*the exact original IF frequencies (i.e. strong local BC
*station on 1600 kc) which might explain why the xtal
was chosen for 1800 kc instead of 1500 or 1700.
We have a local mid power station at 1600KHz, WWRL, at my parents' house,
so my father might have wanted to avoid problems with it.
His radio had a bandswitch instead of plug in coils, and he'd receive
various broadcast SW stations. *He wasn't a ham at the time just yet. *
I had a friend who was a retired engineer with GE turned TV tech who
built
one with a band switch and he later modified it to
be more of a general purpose SW receiver. His name was Olin Griggs.
Jimmie.
I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. *The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. *I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. * Maybe they could be cleaned up, but it no longer
seems worth the effort. *My new idea is to use miniature relays to
switch the circuits. *I recently found nearly a gross of small relays
for free so why not?- Hide quoted text -

- Show quoted text -

I tried the TV tuner trick one time and it didnt work well at all.
Most tuners are tossed because the contacts fail. ...

Not really. Back then TVs were often tossed because the flyback xfmr had
blown and repair was deemed uneconomical. Or someone said that because
in reality they wanted that brand spanking new set that was one sale.

But this is so long ago that if there's any left the contacts will have
corrodes away.

[...]

--
73, Joerg- Hide quoted text -

- Show quoted text -

You must be younger than me, Ive replaced a lot of TV tuners and
flybacks. It was in the early 80s that i first noticed
TVs becoming diposable and quit working on them. Luckily for me there
was still a lot of other electtronic repair work needed to be done.
Most of the local industry was becoming more electronic oriented in
their equipment and needed someone to maintain their equipment but did
not want to hire a full time tech. The sawmills, textile plants, food
processing plants kept me pretty busy aand i enjoyed the work much
more not having to deal with the usual customers.


Jimme

Was my father's homebrew double conversion SW receiver a HBR?
 

JIMMIE wrote:
On Mar 21, 5:11 pm, Joerg
wrote:
JIMMIE wrote:
On Mar 20, 6:47 pm, ken scharf wrote:
JIMMIE wrote:
On Mar 18, 9:24 pm, Robert casey wrote:
The design used plug-in coils for the osc and rf stages, and
they were double conversion designs, with a first IF of
1600 kc and a second IF of either 100 kc or 85 kc (when
using surplus ARC-5 IFTs.) The 1800 mc xtal you bought
your dad was used for the second coversion osc. to convert
the 1600 kc IF down to 100 kc. Many hams deviated from
the exact original IF frequencies (i.e. strong local BC
station on 1600 kc) which might explain why the xtal
was chosen for 1800 kc instead of 1500 or 1700.
We have a local mid power station at 1600KHz, WWRL, at my parents' house,
so my father might have wanted to avoid problems with it.
His radio had a bandswitch instead of plug in coils, and he'd receive
various broadcast SW stations. He wasn't a ham at the time just yet.
I had a friend who was a retired engineer with GE turned TV tech who
built
one with a band switch and he later modified it to
be more of a general purpose SW receiver. His name was Olin Griggs.
Jimmie.
I once saw an article in 73 magazine showing a HB receiver that used a
re-worked turret tv tuner as a band switch. The coils were re-wound
onto the original forms, but some have just replaced the forms with some
of the smaller sized toroid cores. I have a bunch of old tv tuners in
the junk box, but over the years the contacts have gone bad and now show
a high resistance. Maybe they could be cleaned up, but it no longer
seems worth the effort. My new idea is to use miniature relays to
switch the circuits. I recently found nearly a gross of small relays
for free so why not?- Hide quoted text -
- Show quoted text -
I tried the TV tuner trick one time and it didnt work well at all.
Most tuners are tossed because the contacts fail. ...
Not really. Back then TVs were often tossed because the flyback xfmr had
blown and repair was deemed uneconomical. Or someone said that because
in reality they wanted that brand spanking new set that was one sale.

But this is so long ago that if there's any left the contacts will have
corrodes away.

[...]

--
73, Joerg- Hide quoted text -

- Show quoted text -

You must be younger than me, Ive replaced a lot of TV tuners and
flybacks. It was in the early 80s that i first noticed
TVs becoming diposable and quit working on them. Luckily for me there
was still a lot of other electtronic repair work needed to be done.
Most of the local industry was becoming more electronic oriented in
their equipment and needed someone to maintain their equipment but did
not want to hire a full time tech. The sawmills, textile plants, food
processing plants kept me pretty busy aand i enjoyed the work much
more not having to deal with the usual customers.


Same here, in the early 80's I began to refuse fixing TVs and stuff. But
even before that, I remember the flyback transformers for some sets
being so outrageously expensive that a repair plain didn't make sense.
Especially if it had taken out the H-deflection tube and some other
stuff with it or the set itself had already been quite tired at the time
it hissed its good-bye. This was in Europe.

--
73, Joerg

Was my father's homebrew double conversion SW receiver a HBR?
 

On Mar 21, 4:31�pm, Joerg
wrote:
AF6AY wrote:
"Joerg" posted on Fri, Mar 20 2009 6:06 pm
ken scharf wrote:
JIMMIE wrote:

Relays are ok in those applications, where there are actual currents
flowing. What I meant was pure signal switching with no DC currents.

That's called "dry" switching in the electronics industry, has been
called that for over a half century.

Sealed relays, Reeds, mercury-wetted and such work quite well there. But
non-sealed versions have issues and a snap-on plastic cap ain't a seal.

Didn't say that that it was a seal. But...there are many kinds of
'seals' and there are many kinds of contact alloys which few hobbyists
investigate.

Those problems became really nasty after we moved across an ocean and
all this stuff was in a sea container for two months. After that almost
all the band switching relays had problems, had to clean all of them.
Now I am down to one sticky relay every couple month or so.

My wife and I own a nice 2005 model Chevrolet Malibu MAXX that we've
driven in both driving rain with some intermittent ice to Wisconsin
from California and back, to Washington state from California and
back. It has two little boxes of many small-signal relays, only a
very few qualifying for large-signal types. Never a problem since we
got it in late June of 2005. Those relay boxes all have lids and the
small relays have little covers and that auto has definitely been
exposed to the environment many times in the last 4 years.

I can sympathize with your bad sea container shipping experience but
consumer-grade radios (such as for amateur radio) were never designed
to be exposed to sea evnvironments. Ask yourself how all those off-
shore made radios made it to the USA? Inside standardized container
boxes.

I didn't make my comment lightly or pretend that I know everything
there is to electronics. I do know, by a rather large set of
experiences that 'dry' circuit relays (hermetically sealed OR by
reasonably-good individual covers) will work without having to be
'operated many times' in order to 'clean their contacts.'

I'll cite one application that is military, the US AN/PRC-104 manpack
HF transceiver. About one-third of that backpack radio is an
automatic antenna tuner so that one whip length can be optimized for
best electrical characteristics. It does that with a rather
conventional microprocessor control driving two banks of binary-
sequence inductance and capacitance values switched by relays. It has
been in operational status with the US Army since around 1984 and is
expected to be phased out soon in favor of more modern HF-to-UHF
transceiver designs. It's been a while since I've seen the guts of it
but I don't recall that it had any hermetically-sealed relays in it.

Right now I'm beginning to start cutting holes for a rebuild of an
'ancient' HF receiver once made for my late father wanting to tune to
some SW BC stations, principally Radio Sweden back in 1964. I've been
fortunate to get a large collection of North Electric small sealed
relays dating back to about 1955 production which I've already
breadboarded for bandswitching use. Very familiar with relay testing,
I found NO problems from 'dry' contact switching. The low capacitance
to ground and minimal series inductance from the contact set do NOT
upset any of the L-C circuits being switched.

replaced with PIN diode circuits and that, of course, made the issues
completely go away. But it's always a hassle to do in an exisitng circuit..

Yes, I have that in the filter board of my two decade old Icom IC-R70,
all switched with 'RF switch' diodes (no registry number). If needs
be, that entire filter board could be enclosed to prevent any problems
from the environment. Icom used that sort of semi-conductor switching
for ease of overall parts cost along with reduced labor costs to
Icom. Such work fine at the LOW impedances involved (50 to 75 Ohms)
but I've tried to duplicate that at 10 KOhms on a breadboard and have
run into problems with diodes' own impedances affecting circuit
operation. Those could be solved, I'm sure, but I didn't care to
spend weeks fiddling with them for my rebuild project. The relay
contact set had only the shunt capacity and series inductance to
contend with and those were very low values and easily compensated for
alignment.

73, Len AF6AY