SW receiver

Hi,
a reflex stage is often hard to be tamed. A reflex regen is even harder. A pentode (without reflex, the amount of feedback regulated by DC on G2) seems to be a better solution.
A superhet is always more complex than a simple regen (it contains an oscillator/mixer, IF filter etc.), so its performance vs. complexity ratio tends to be worse.

BR from Ivan

hi ,
i do have the schematic of the radio in printed version. I do not plan to restore it. From what i heard  it was produced by Tehnoton Iasi, and the story says that the "best " receivers where built by Electronica Bucuresti in this country .  

By the "best " i mean the ability to receive even the slightest available signal , good selectivity ... and so on, you know , the radio part not the audio part like HIFi output speakers and things like that. 

Anyway i had a suspicion that the valve radio would come up in the top among some digital receivers . 
I am not making diy receivers anymore , no time for that. I did try a single valve radio once . The tube vas ecc83 i think . It hat 2 triodes. It was reflex and reactive type combined. It used the first triode as rf amp and audio amp but it also had a feedback loop to the input LC circuit by means of a coil supplied trough a pot from the anode. That was quite selective but not sensitive at all . If the reaction given from the pot was not in the exact right amount , the stations could not be heard given from the weakness or by the radio oscillating by itself and covering the signal. This type of circuit requires a lot of skill by the operator . My conclusion back then was that super heterodyne are on the top, although  i never been able to build one.
 I did had in my hands a  receiver with semiconductors called OKEAN 222 ( was written in Cyrillic on the radio) which i consider quite good , it received a lot of stations and i believe it was somehow digital . At least the band switching part and it had no variable condensator , the stations where looked up with a potentiometer. Inside the radio looked like pure art for me , the pcb the components ... and outside the radio looked also cool , somehow ahead of its time

zsolt wrote:Hello , 
shortly i found a small little radio called SOLO500 . The radio has 4 bands , LW, MW,SW and FM.
...

Hi zsolt

The schematic was found here:
https://elektrotanya.com/radio_tehnoton_solo500.jpg/download.html#dl

TBA570A datasheet is here:
https://datasheetspdf.com/datasheet/TBA570A.html

enjoy

Thank you, Glenn,
it is A LOT of brain food!

VBR from Ivan

Ivan wrote:Considering the performance-to-complexity ratio, the best RX ever is IMHO a single tube regen.

Hi Ivan

How about this one - but no tube is used - only a single transistor (and a RF-amp; also one transistor) :-)

A 1.2-volt Vackar-style minimalist regenerative receiver: Design, analysis, and implementation (updated 2017/05):
http://qrp-gaijin.blogspot.dk/2015/08/a-12-volt-vackar-style-minimalist.html
backup:
https://web.archive.org/web/20180226205208/http://qrp-gaijin.blogspot.dk/2015/08/a-12-volt-vackar-style-minimalist.html
http://1.bp.blogspot.com/---Zk3BzGY6U/Vdlqr-suY_I/AAAAAAAAAT8/PXHfTZe_ipM/s1600/regen-circuit.png
https://web.archive.org/web/20180128061212/https://www.qsl.net/df7tv/datasheets/1SV149.pdf
1SV149 Toshiba ca.= BB112 ca.= KV1236

BB112 17-560 PF 12V. 8V 20pF; 1V 500pF
KV1236 26-490PF
BB212 22-560pF (= 2*BB112)
BB130 ca. 15-500pF 1-28V = KV1225, KV1226
1SV102 ca.= BB130 high Q

.

Extremely simple - but no quenching? Regen quenching is mandatory?:

See:
Fig.8 Regenerative receiver for the MW AM broadcast band:
http://www.zen22142.zen.co.uk/Theory/neg_resistance/Oscillations%20and%20Regenerative%20Amplification%20using%20Negative%20Resistance%20Devices.pdf
backup:
https://web.archive.org/web/20180128032426/http://www.zen22142.zen.co.uk/Theory/neg_resistance/Oscillations%20and%20Regenerative%20Amplification%20using%20Negative%20Resistance%20Devices.pdf

.

Or this one:

A Shortwave receiver with automatic regeneration control:
https://web.archive.org/web/20170718183222/http://zpostbox.ru/a_shortwave_receiver_with_automatic_regeneration_control.html

.

Best - with tube?:

Frequency compensated LC networks for oscillators with the wide tuning range:
http://www.kearman.com/vladn/hybrid_feedback.pdf
https://web.archive.org/web/20161022044737/http://www.kearman.com/vladn/hybrid_feedback.pdf
Quote: "...
Notes for the Rs+Rp mixed loss model plot (middle):
Nearly perfect zero-tilt for a mixed Rs+Rp model. The LC network values can be tuned to achieve exactly zero tilt for any given combination of Rs and Rp (not possible for classes 1, 2 and 3 alone).
Note nearly constant Q for the mixed load model.
...
All three hybrid feedback oscillator prototypes built in this study confirm that after properly balancing the two feedback paths the oscillation onset happens at exactly the same gain settings at the two opposite frequencies of the tuning range (or any two frequencies of choice) and that the remaining non-linear term of the threshold dependency is quite small.
...
The end result was a surprisingly well behaved regenerative receiver. It has a very good frequency stability and does not require adjusting regeneration level as you tune from 3.3MHz to 9.1MHz which is highly unusual for a conventional regen. The oscillation threshold level is so flat that it is completely feasible to have just two fixed regeneration presets - one for AM and a higher one for the SSB/CW modulation types. To illustrate these somewhat unconventional results I put several videos on youtube.
The two most relevant to the subject of this discussion are:
..."
http://www.kearman.com/vladn/hybrid_theory.pdf
https://web.archive.org/web/20210211011108/http://www.kearman.com/vladn/hybrid_theory.pdf

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Maybe with this extra feature?:

A Receiver That Laughs at Static:
http://theradioboard.com/rb/viewtopic.php?f=4&t=7171
Using two loops to cancel distant and local noise:
http://theradioboard.com/rb/viewtopic.php?t=7027

Considering the performance-to-complexity ratio, the best RX ever is IMHO a single tube regen.

zsolt wrote:
...
And buy the way , which is in your opinion the best SW radio receiver ever built ?

Hi zsolt

What do you mean by "best"?

Portable/stationary?

Sound quality above all?

How simple it is to use?

Price - does it matter?

Do need AM only - do you also need SSB - and maybe DRM?

Selectivity?

Tolerate strong signals?

All SW from 1.6-30 MHz - or only some frequency interval?

rechargeable battery?

DIY SW receiver?

(best antenna)

(QRM-Eliminator?)

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Users writes reviews:

Review Category: Receivers: General Coverage:
https://www.eham.net/reviews/view-category?id=8

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From around 2014:
N9EWO tests 3 Chinese Portables.
Sangean ATS-909X (including Radio Labs version)
Tecsun PL-660
Tecsun PL-880
https://web.archive.org/web/20171014015631/http://webpages.charter.net/n9ewo2/ats909x.html
Quote: "...
Built in automatic battery recharge circuit for internal 4 AA ni-mh batteries (not included).
...
If SSB is important to you, the Sangean RadioLabs "ClearMod" model is the clear winner to our ears and eyes.
..."

Tecsun PL990 Digital Worldband AM/FM Shortwave Longwave Radio with Single Side Band Reception & MP3 Player, Matte Black:
https://www.amazon.com/PL990-Worldband-Shortwave-Longwave-Reception/dp/B08KL77Q4H
Quote: "...
The Tecsun PL-990 is the latest top of the line Tecsun shortwave radio receiver that equipped with an analog High-IF circuit and DSP triple conversion decoding technology. This radio receiver has great performance in sensitivity, selectivity and combating interference of mirror stations (image rejection).
..."

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SW transceivers:
Ham Radio Products:
https://apache-labs.com/1001/Ham-Radio-Products.html

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DIY:

Cheap very high level mixer made with analog CMOS switches - output can also be MF= 41MHz, 10,7MHz or 455kHz:

Dan Tayloe:
http://www.wparc.us/presentations/SDR-2-19-2013/Tayloe_mixer_x3a.pdf
https://web.archive.org/web/20170308040429/http://www.wparc.us/presentations/SDR-2-19-2013/Tayloe_mixer_x3a.pdf

Very linear AM-detector:

"High-fidelity" AM broadcast detector:
http://g3ynh.info/circuits/hi-fi_am.html
A linear high-frequency voltmeter and AM detector:
http://g3ynh.info/circuits/AM_det.html
http://g3ynh.info/circuits/push-pull_det.pdf

Relatively simple DIY AM MW receiver with "High-fidelity" AM broadcast detector:
http://g3ynh.info/circuits/Bob_Batey/am_hifi_shet_sch.gif
https://web.archive.org/web/20171022023744/http://g3ynh.info/circuits/Bob_Batey/am_hifi_shet_sch.gif

The HF7070 HF/LF Communications Receiver Prototype.
A detailed look at high performance receiver design:
http://www.arrl.org/files/file/QEX_Next_Issue/Jul-Aug_2013/QEX_7_13_Horrabin.pdf
Backup:
https://web.archive.org/web/20170318044254/http://www.arrl.org/files/file/QEX_Next_Issue/Jul-Aug_2013/QEX_7_13_Horrabin.pdf
Quote: "...
There is suspicion that close-in phase noise within the PLL bandwidth on the HF 7070 is limited by band-gap noise on the phase detector chip made by Philips: the 74HCT9046. [74HCT9046 (up to vcenter 17MHz) is a heavily improved CMOS 4046 (up to vcenter 2,7MHz)]
...
Figure 4 — This graph shows the measured dynamic range (DR) of the HF7070 prototype receiver. The reciprocal mixing dynamic range was measured with a 2.4 kHz bandwidth. Notice that the 2nd order IMD DR is completely flat across the entire measured range. The 3rd order IMD DR increases rapidly above a signal spacing of about 5 kHz and then becomes quite flat at a signal spacing of 20 kHz. Ideally, the IMD DR should not change as the signal spacing of the input signals changes. This radio has a 3rd order IMD DR that is better than 110 dB at 20 kHz spacing, and levels off at 115 dB, which is quite remarkable. This graph was copied from Martein (PA3AKE) Bakker’s website: http://martein.home.xs4all.nl/pa3ake/hmode/ar7070-proto2.html .
..."

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QRM-Eliminator / "Noise Canceller":

A Two-Transistor Phaser for 80 – 10 meters (update March 2019 of 2006 design):
http://www.pa0sim.nl/Phaser%2080%20-%2010%20meters.htm
Quote: "...
It is possible to get an almost perfect linear phase shift when using this circuit for both antenna signals. How: by controlling the phase shift of both antenna signals in the opposite direction at the same time with one single knob.
The next schematic shows the basic new transformed circuit using a differential capacitor (Ca and Cb [could variable-capacitance diodes be used instead?]) for tuning the phase shift. A variable capacitor makes a much better control than a variable resistor (contact wear out).
...
Because of the much better control of the phase difference and the gain ratio, it is much easier to get deep nulls.
..."

Hi Zsolt,
it sounds like you encountered some sort of fading.


VBR from Ivan

Hello , 
shortly i found a small little radio called SOLO500 . The radio has 4 bands , LW, MW,SW and FM. After some trouble with starting it up i found that FM, MW and LW are garbage but the SW is quite a big wide world . All kind of stations in all languages came in , i stopped at a station that was playing some weird pleasant instrumental music , after half an hour when it stopped i found out that is radio China 
Anyway , the interesting part of the experience was the sound quality going from good to bad , like now is excellent and after ten seconds bad . Without not even touching  the radio the reception was oscillating between the two . It seemed so natural like sinusoid .
And after tuning the scale a few cm away the same station came in weaker but steady 
What can (you)  old clever radio foxes tell about this ?
And buy the way , which is in your opinion the best SW radio receiver ever built ?