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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

First, the legal issue: in the US, it's not legal to transmit on GMRS frequencies on a radio not type-accepted for GMRS. Having an FCC ID doesn't mean that a radio is type-accepted for GMRS; UV-5Rs aren't. Also, 462.55 MHz is slightly below GMRS channel 1, so you were transmitting out of the band. At 8 W, you should have been able to easily have a ...


4

The antenna is most like a Planar Inverted F Antenna, or PIFA. Wikipedia has a brief introduction to them. Here is my sketch of a classic example: The PIFA is a wider bandwidth version of the IFA, distinguished by a radiator parallel to the ground (the upright of the F), a shorting bar at one corner or edge (the top of the F) and the feed a short distance ...


3

First, some technical information. According to W8JI, who knows more about antennas than I likely ever will, a 5/8λ vertical antenna potentially offers a few decibels of horizontal gain over a 1/4λ vertical, if you have a large-enough ground plane; specifically, a ground plane with a radius of about 1.5 m or larger. That's a ground plane 10' across, in ...


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 ...


2

Ask the radio shop to show you the VSWR of the antennas at the frequencies you use. Have them do it in front of you. That will likely tell you whether the antennas are suitable or not. To ensure an accurate measurement, the antenna must be plugged directly into a VHF (not CB) SWR meter with no coaxial cable jumper between the antenna and the meter. A ...


2

A quick note: If the transmit system described in the OP will be or is unlicensed by the regulating body having jurisdiction for such (e.g. the FCC in the USA), then some risk will be involved in its use. In the US, such unlicensed systems in the FM broadcast band are authorized under title 47CFR §15.239, but limit the maximum field intensity 3 meters in ...


2

You've already been apprised of the legal issues, so let me ask you a few questions... How did you program the radios? Were the antennas screwed all the way in? What was the terrain like where you were testing these things? Trees, houses? How did you decide on squelch level 5? Did you modify the CTCSS settings on either of the radios? This seems like the ...


1

Some (in fact quite a few) mobile antennas are effectively an "end-fed" design rather than a "ground-plane" design. One way to identify them is that they will generally have a noticeable transformer coil at the bottom (usually enclosed) to transform the impedance. If an antenna's description includes the words "ground-independent&...


1

SSB requires a signal from the microphone: only when you are talking there is a signal generated. For CW you need to connect a morse key or paddle to have output signal. When FM and AM are operational there is nothing wrong with your power amplifier. In case of a defect: check the microphone by listening to the AM or FM output signal and when that is ok and ...


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

The battery inside the radio is almost certainly a lithium-ion type (one to three cells, most likely one or two), which requires the device to manage its charge (for safety, as well as for battery cycle life purposes). That means that not only is there most likely some regulation in the charging cradle (even if the cable from the wall wart is DC -- and it ...


1

Check out this video from AG6IF who built a 2m slot antenna out of an old parabolic dish. His application was for home mounting a stealthy antenna, but the interesting notion there is that the slot is curved. His video shows a chart from an analyzer as well. This indicates to me that it's worth trying your idea too. Hope this is helpful!


1

On a vehicle with a steel body and roof, the most feasible 2 meter slot antenna design is a pair of square flat plates with spacers to maintain the space between them. The slot ends up being the horizontal space between the plates. The top plate is connected to the center of the coax feed line, and the ground is the bottom plate to which is joined the ...


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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