6

If I understand the description correctly: simulate this circuit – Schematic created using CircuitLab If that's all it is, I wouldn't say it's any big deal. Whenever you have multiple paths to ground, current will split between them. It's these currents that keep "ground" approximately the same voltage everywhere: an essential assumption in the ...


5

I used LiFePO4 (read: Lithium Iron Phosphate) for my dad's FT-891. The big advantages of LiFePo4 are: Very power dense, almost as much as Li-Ion, IIRC twice as much Wh/kg than Lead-acid Extremely safe: they don't short circuit themselves to flames, like Li-Ion does Flat voltage discharge characteristics: their nominal voltage is 3.2V and they stay at 3.2V ...


4

An anecdote: I had problems with my station which included computer-radio interconnections; some of my devices (RTL-SDRs) would lock up when I powered on my Yaesu FT-897. I eventually tracked this down to the power-on inrush currrent of the radio passing through coax shields and the chassis of the antenna switch that both were connected to. I solved the ...


4

It makes a difference of: $$ 10 \times \log_{10}\left(3 \over 5\right) = 2.2 \:\mathrm{dB} $$ How big is 2.2 dB? See How big is a decibel? It's also relevant to note: if the 12V battery is lead acid, the charged voltage can be as high as 13.7. Furthermore, while a boost converter might further increase your transmit power, it's likely to make noise which ...


3

If you haven't done much QRP operating, QRP is a funny thing. Sometimes propagation is great, and you wonder why anyone would bother with 100 W or more. I'll never forget my first DX QSO, from Oregon to Estonia, running 11 W to a vertical, by gray-line propagation at the bottom of the sunspot cycle in 2006. Other times it seems like a complete waste of ...


3

When they installed solar on my house, I lamented how Hurricane Sandy came, and yet all of the people having solar on their house could not use it because of the anti-islanding law(s) which say that your solar system, which usually pumps its excess power into the grid, must not do so when the grid is down, to prevent from electrocuting electric company ...


3

Sealed lead acid batteries are heavy. I would not recommend them. lithium phosphate or lipo are lighter, but can be hazardous. in case of physical damage to the battery they can burst into flames or even explode. Lithium Iron Phosphate batteries are also light weight and are much safer. Bioenno is a well known battery vendor that has a wide selection of ...


3

I wouldn't risk directly connecting a 9.6v battery to a radio that expects 5-6v. The simplest solution would probably be the diodes mentioned in the comment to your question, but as the battery voltage dropped the voltage reaching the radio would drop as well, and as the battery got low the output voltage after the diodes might be too low to power the radio,...


2

You can do quite a lot with the RTL-SDR as a "spectrum analyzer". A proper spectrum analyzer will be accurately calibrated to measure absolute power, but if you can fix the gain of the RTL-SDR and the receiving software you can use it to make relative power measurements which are sufficient if you only want to roughly quantify linearity. You could dump the ...


2

Super-Light intro to nonlinearities Amplifier model Ideally, an amplifier has this output function $f(x)$, where $x$ is the input amplitude: $$f_\text{ideal}(x) = a_1 x\text,$$ and we call $a_1$ the amplitude gain (which is inherently the square root of the power gain). Sadly, real amplifiers don't have ideal behaviour, instead they have: $$f(x) = a_1 ...


1

Generally QRP is considered to be 10 watts or less. A small RF amp could get your 3 watts up to 9 which would be a more powerful signal but this is something you would have to homebrew. You can get the power needed to drive this transceiver and amp by wiring the batteries to increase the voltage to the level required, (series vs. parallel wiring). This all ...


1

Galaxy, there are a number of things to watch out for when connecting power to your Cobra 29LTD AM only CB radio. The power supply must be a regulated DC power supply, which outputs between 12 and 14 V DC. An adapter which outputs AC is no good. Note that many adapters like the one in your picture are not regulated, and when nothing is connected to them ...


1

CB radio service transmitters are limited to 4 watts output power. Figure that that output circuit is only 50% efficient at most, and in round numbers you'll need probably at least a 10W input if not more. For DC circuits the power (watts) is equal to the voltage times the current (amps). Your 12V, 0.3A adapter is therefore rated to supply 3.6 watts which is ...


1

You might be guided by the circuit for the Ameritron RCS-4 Remote Antenna Switch. I have used this unit on HF for decades without any noticeably deleterious effects, though I have never performed any measurements. The manual shows L201 and C203 filtering the supply to the relay coils. L201, p/n 409-2150, is a 1A 90uH choke. At 1.8-MHz, this provides about ...


1

If you want 20 A, then lead-acid batteries will be too heavy. You would want some kind of lithium-ion battery. Lithium ion phosphate batteries are popular for this sort of application, like the kind that Buddipole sells. A few caveats: all this stuff will be really heavy by backpacking standards: the radio alone weighs 2.45 kg (5.4 lbs). Of course there'...


1

Should a 'a not so good contact' at the HT's external jack/plug be ruled out as a contributory factor, the only way to avoid DC current in the coax braid would be to have a separate battery pack for the HT. The moot point is whether DC current in the braid does matter.


1

Very simple. Never connect Negative directly to battery and never fuse the Negative as doing so is extremely dangerous. Doing so puts your radio in Parallel with the Battery Bonding Strap to the chassis. That means a portion of all the automobile electronics systems current is flowing through your radio including the Starter. Secondly will bypass the vehicle ...


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