HEATHKIT HR-10 ADD JUNK!

[@wa7sca]

I was looking for ways to improve my HR-10. The Q-multiplier is perfect. Thank you!

[@MIKROWAVE1]

Great! This can pep up the old receiver.

[@BillyLapTop]

Wow, that was a real flashback for me when you popped out the 1964 ARRL Handbook. That was my first handbook purchase and I got it at Parts Unlimited in Bloomfield, NJ. That was a big day for me. One of the features of that handbook I loved and other editions of the handbooks published by ARRL, were the ads in the back pages. A great bit of nostalgia. FB on the Q project and converter. Great stuff!

[@MIKROWAVE1]

Everyone has that first Handbook moment - those first ones set you up. Mine was a dog eared 62 Handbook given to me by my neighbor Elmer followed by a "modern" 1973 edition.

[@W1RMD]

Nice looking radio and projects! You're a wealth of information and have given some great ideas for future projects. Weird that they use the marine ssb calling and distress frequency (2182) as an if. Thanks for sharing and 73's!

[@wa9kzy326]

Fantastic demo of "Q" multiplier. I made contacts on all bands, barefoot, with my HR-10.

[@MIKROWAVE1]

Um - the bands worked better with sunspots!

[@PapasDino]

I remembering lusting after the HR-10/DX-60 "twins" back in the day! TNX for sharing. 73 - Dino KL0S

[@MIKROWAVE1]

Lust is the right word! My buddy had the HR10 and DX-40 combo.

[@QESPINCETI]

My very first HAM RX.. way back in the late '60's. It was real Fun building it and then building the DX-60, etc.

[@MIKROWAVE1]

A classic Novice station indeed! Lucky!

[@msf60khz]

I had a converter using a GG stage with untuned input followed by ECH35 triode-hexode mixer, and it worked well even at our UK 70MHz band (using a crystal-multiplier stage). Your Q multiplier works beautifully.

[@kenwilliams563]

I had the Heathkit RA 1, made in the UK, covered all the UK bands only, and came with a pre-aligned front end manufactured at Ace Radio in Rhyl North Wales where I worked. I also had the Heathkit Q Multiplier on a different radio

[@MIKROWAVE1]

Wow that is a more modern version of the radio with 160M! Never seen this side of the water.

[@QESPINCETI]

Gosh i forgot about that crystal calibrator and later.. the external VFO too!! A real challenge staying in frequency and inside the ham bands.

[@MIKROWAVE1]

Yes and the Official Observers and FCC sent me fan mail as a kid.

[@mohinderkaur6671]

6j6-6ak5 was well used in the 50s arrl hb. rca did a of 6j6 vhf in tv

[@ktheis1]

Wish I had a Q-mult as a novice in the ‘70’s. My HR-10 was all but useless on 40 at night due to the dozens of cw stations in the novice bands. My radio was also deaf on 15 and 10 - a preamp helped but again, with the wide bandwidth it was tough to use.

[@msf60khz]

I remember that a Q-mult could be coupled to the IF stage using just a very small capacitor, no need for a second coil. Thanks for interesting video.

[@MIKROWAVE1]

Yes if the unit is located close enough, or if the capacitance of the coax feed can be tuned out with the existing IF can. The second coil simply makes the coax feed invisible when you disconnect the Q-multiplier.

[@hank1519]

Wonderful video! Thank you so much. Very pleasant to watch and easy to understand.

[@MIKROWAVE1]

Thanks for watching!

[@gumbykevbo]

The Q multiplier circuits you showed are certainly (nearly) oscillators, but I would not identify them as Colpitts, or even close cousins. A Colpitts osc. typically has a non-inverting amplifier with a gain just under unity, a cathode (or emitter) follower usually. This drives a tuned circuit configured as a capacitive voltage multiplier (X2 usually) to provide the required >=1 loop gain to sustain oscillation. The split capacitance is driven at the center, and the output taken at the top. In this case the tuned circuit input and output are in phase, giving 0 degrees phase shift around the loop, thus positive FB to sustain oscillation. In the Q multiplier circuits shown, the split capacitance is grounded in the middle. ( which can be re-drawn and identified as a pi network.) It is driven at one end of the coil, and the output taken off the other end. In this case it is functioning as a phase inverter, which is needed because the tube is configured grounded cathode, so it also inverts, thus a second inversion is needed to provide 360 degrees of phase shift, and thus positive FB to sustain oscillation (or nearly so in the Q-mult.) One downside to these circuits is that the tuning capacitor only changes one half of the split capacitance, thus the voltage gain (loss) of the tuned circuit changes with tuning, disturbing the FB level. As the loop gain needs to be set very near unity for highest Q multiplication effect, this interaction is a bit unfortunate. I see two ways to address this issue: 1) A split tuning cap could be used so that the ratio is maintained. In this case the frame/rotors of the tuning cap can be grounded as in the example circuits. 2) A coil with a grounded center tap coil could be used, and a single capacitance placed across it. In this case both sides of the variable tuning cap would be floating WRT ground, which can be troublesome in it's own right. 73, ko0b

[@MIKROWAVE1]

Very interesting. Please keep going and discuss negative resistance in this context.

[@gumbykevbo]

@@MIKROWAVE1 Negative resistance means that the Q-multiplier draws less current as the signal voltage increases, and more as it decreases....but only at the tuned frequency, which is where the positive FB of the oscillator is nearly unity. This can happen because a small IF signal causes the near-oscillator to respond with it's own slightly larger signal. The combined circuit will oscillate if the net resistance (Q-mult + RX) is actually negative...so the Q-multiplier's negative resistance is used to cancel most, but not all of the resistance in RX IF filters. The QM oscillator is loaded by the RX IF enough to avoid oscillation of the combined circuit.

[@wa4aos]

Can the converter be adjusted to somewhat match the 15 meter dial scale??

[@jimeppright7862]

Never saw a Q mult work well with an IF above about 2 mHz. Is there a secret circuit I don't know?

[@bundylovess]

Awesome series of videos mate big thumbs up 👍

[@СтаМилАлас]

Bravo, 73 yu 1 qg

[@krzysztofszmel7503]

bardzo sa ciekawe twe filmy,pozdrawiam.

[@MrDonJBerg]

Any way to take the Heathkit Gr-125 Q mulit. and convert it to the 1680 IF??

[@MIKROWAVE1]

Yes I would assume so, and I happen to have a 125 and one of the older units as well that could be the basis for a project and video for 2020.

[@MrDonJBerg]

@@MIKROWAVE1 The variable cap is the same value, and I have to old coils laying around and 5 HR-10s to fix and sell. Would love to get some insight as to which parts to change and to what value. The schematic is just about the same as yours

[@cannong1728]

want to sell it?

[@yardleybottles6025]

Now I know not to buy the HR10! LOL

[@MIKROWAVE1]

It's not for everyone! Ha. I still like the look though.