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axorlov

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Everything posted by axorlov

  1. And why do you think it is exactly 0.20μV over 50 Ohm load? I'll tell you, it's because this value roughly corresponds to the difference that can be detected by human ear after some "normalized" amplification. RST (RS) scale is about psycho-acoustics, not about electronics at all.
  2. I did not say that^^^^ I'll try again. One S-unit is when human ear can tell the difference between levels of AM signal. For FM demodulator the readability is how clear it can detect frequency/phase shift. Demodulator does not care about amplitude, and long as it has enough of it to detect frequency shift. Deviation plays bigger role than amplitude. S-units on RST scale are for amplitude. If you want to create RST scale for FM, the one S-unit (when human ear can tell the difference) will not be 4x of the power sent through the transmitter.
  3. This RST scale/standard was developed 90 years ago to parametrize decoding of Morse code (continuous wave modulation) with human ear. It is not applicable to FM demodulators. We've been through this already, and I don't want to pollute this thread. But we can start a new one.
  4. Good form is to use monitor function for a second or two, and/or look at the activity LED that most HTs have. LMR (Part 90) radios have Busy Channel Lockout feature, which is also can be used. Stomping on somebody's conversation is a bad form, indeed.
  5. Yes, but only because repeaters, usually, located high off the ground, providing longer line-of-sight distances. And also because repeaters, usually, have much more efficient antennas and much better, by many parameters, receivers. There is nothing magical about repeater, and repeater created from two HTs placed at shoulder height will have less reach than same radios on simplex.
  6. I would refurbish NiMH battery. I'd try to pry it open carefully, and replacing old cells with new ones. You will be able to keep the charger, and it will be much cheaper than using Lithium cells. I'd buy the cheapest ugliest battery off ebay to try out this lobotomy. In fact, I did it before to some laptop batteries (they were Li-Ion 18650, but the idea is the same).
  7. In other words, RF radiation is doing good to human gene pool, be creating a selection pressure that makes babies of aforementioned individuals less likely to survive. Not by the direct effect. Cool!
  8. Some fine oscilloscopes in Health and Fitness category. Well, in a big picture, maybe it is a correct classification.
  9. Dammit, how did I not know Goodwill has it's own auction site! There are also some incorrectly classified items, like PRO-2035 in home electronics\receivers, just a heads-up.
  10. Advantage of Ed Fong antenna is that you also get 2m. So, if you can live with common mode current, more power to you. But for GMRS only there is Browning BR-6140, which was cheaper(!) than Fong at some time in the past, has proper choke, N connector, sold with mounting hardware, and is only 24" long. It is unity gain antenna, like Fong. I had very good results with it. SWR was low, below 1.3:1. It did not demonstrate common mode current. Currently I mounted Diamond X50NA, because I'm more interested in ham 2m, it has crappy 2:1 SWR on GMRS, but it works for me at this moment of time. My antenna system is evolving. The poor man method to test for common mode current: plug SWR meter between radio and antenna, touch with your finger the connector on the antenna side while transmitting. If SWR changes, you've got significant common mode current. In my book (and only in mine) if the change is 10%, it's fine. If it's between 10% and 30% I may address it, depending on how much trouble it involves. Over 30% is a problem needs fixing.
  11. J-Poles demonstrate high common mode current, much more than dipoles and much-much more than 1/4 waves with ground plane. This is the reason Ed Fong antenna is a lousy choice if mounted on metal mast, SWR is all over the place because of coax coupling with the mast. Why more than one, look here at Figure 3: https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection On UHF frequencies, their sample bead has only 80 Ohm impedance, and you want much more, maybe 600 Ohm. And on UHF frequencies multi-turn toroid chockes also do not work because of capacitive coupling between turns.
  12. Should be easy to verify if radio actually transmits with wattmeter between radio and antenna, or better, between radio and dummy load.
  13. With Ed Fong antennas you need ferrites, and a lot of them. Sweet spot seem to be between 5 and 7. But if SWR does not change when you manhadling the cable, whatever number you have is good already.
  14. Everyone is taking a cheap shot at 900MHz MURS . I tell you what, the 900MHz frequency hopping radios from Motorola (DLR and DTR series) is a perfect way to talk to wifes. Not only to your wife, but somebody else's too. They are actually somewhat secure with 10000 hopsets, and work like a charm. We have a few threads on them, at 900MHz forum.
  15. I see a confusion between the owning a ham license and not owning a common sense and manners. Different things, really. If you can magically ban all hams from GMRS repeaters, you'd still be stuck with local lunatics and know-it-all a-hole youtube influenzers. And they are plenty around!
  16. That is little more complex. The short answer is: Yes, you can transmit simplex FM (I presume) between 144 and 148 MHz. But by blindly doing so, you will piss off quite some number of people, depending on your location and how the air is congested. While the Amateur Band Allocations is the Law, there is also a gentleman's agreement called a Band Plan. Here are Band Plan in US: http://www.arrl.org/band-plan Look for 2m. They do vary locally, depending on how many users doing what exactly. Speaking of 2m, there is a national calling frequency (FM) 146.52 MHz and several frequency ranges dedicated for FM simplex. These are not the law, but an agreement.
  17. Short answer: No, you can not. You are only allowed to used frequencies that are allocated for Amateur Radio (if you have Amateur Lincese). 158.452 is not one of them. Long answer: For starters, see the frequency allocations: https://en.wikipedia.org/wiki/Amateur_radio_frequency_allocations and http://www.arrl.org/frequency-allocations Or in graphic form: http://www.arrl.org/graphical-frequency-allocations
  18. Out of 120 repeater pairs (442-445) can't find single available pair? Wow. I know, there is a very live and dense 70cm scene between LA and San Diego, but still... 120 pairs are available. Edit: they go by 20KHz bandwidth, so there are 150 pairs available. On SCRRBA website they only list 21 pairs. I'm curious, where all the spectrum went?
  19. The V2.0 version of TK-880 came in three frequency splits: Type 1, 2 and 3. Only Type 1 has a good split for GMRS and also has Part 95 cert. Brochure is here, look at the last page: https://www.ameradio.com/doc/Kenwood_TK-780(H).pdf On the label on the back of the radio it would say: TK-880H-1 (or -2 or -3) and V2.0. Radio works and can be programmed to both wide band and narrow band per channel basis. I.e some channels may be programmed to narrow and some to wide in the same time. It is not going to be a whole radio switch to wide band. Programming is similar to Chirp in the sense that there is a list of "channels" - memory slots that are configured to frequency, split, RX and TX tone, name and other options. There are also "zones" that a groups of channels. But there are features that are usually not present in Chirp, like Operator Selected Tone, ability to reprogram buttons on the face of the radio. It also can be programmed to listen to LTR trunking systems, if you have them around and so inclined. Label, this is for 880, not 880H, but you'll get the idea:
  20. I do not have personal experience with TK-890H, just note that it's 100W radio, while max power allowed on GMRS is 50W. Be a good neighbor. Software seems to be available around, KPG-44D. I have personal experience with another radio currently selling on this site, TK-880H. That one is very straight forward to program, and also has Part 95 certification (judging by the published split, it must be "-1", which has Part 95), if it is important to you. Software is KPG-49D, front panel is not remotable. All what was said about passwords and such applies.
  21. KAF6045 gave very clear correct answer. In voice applications (including phone network) it is usually only 300-3000Hz (often 300-2300Hz) is processed, everything else is filtered out. This is why tones are called "sub-audible". And since nothing on this planet is perfect, including filtering, many radios will let you enjoy the higher tones, barely hearable.
  22. It says simply "Wagner orchestra". See, Richard Wagner was a favorite composer of Hitler, and the founder of Wagner Group colonel Utkin (of spetznaz) is a big fan of 3rd Reich. "Wagner" was his nick name during Crimea annexation and later in Donbass, and the private military group he leaded (may be leading to this day) inherited the name.
  23. Wagner Group now recruits convicts from prisons, and sends them into the fire as a literal cannon fodder, promising the full pardon after 6 months of service. However, life expectancy of a random convict there is between one week and two. They (Wagner) burn them like dry hay. No sense to waste expensive radios, Baofeng is the right tool here. According to British Institute for the Study of War, by now Wagner lost about 40000 (forty thousand) as dead, wounded, deserted and POW.
  24. Deficiencies of Baofengs are very well understood and explained everywhere, in countless reviews, videos and instrumented experiments. Their frontend overloads at any sign of in-band or out-of-band RF. Also, when you look at them funny. They work in the middle of nowhere, but fail miserably in RF-congested areas. And also if you look at them funny.
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