Search found 1571 matches

by dyarker
Thu Jun 18, 2020 10:16 pm
Forum: General Discussion
Topic: 4G LTE Interference on OTA Antenna TV
Replies: 16
Views: 439

Re: 4G LTE Interference on OTA Antenna TV

Please read the posts before answering! This discussion was about towers on insulators. Which means RF hot tower. A hot tower needs a spark gap for lightning protection without shorting the signal. My mention of spark gap a couple posts back was for hot tower, obviously a non-hot antenna support tow...
by dyarker
Thu Jun 18, 2020 11:24 am
Forum: General Discussion
Topic: 4G LTE Interference on OTA Antenna TV
Replies: 16
Views: 439

Re: 4G LTE Interference on OTA Antenna TV

The tower you say is 600ft not 2000ft. It supports other antennas so is unlikely insulated at the base. The mountain it is on is not relevant.

The big tube likely is waveguide, or coax.
by dyarker
Thu Jun 18, 2020 10:23 am
Forum: General Discussion
Topic: 4G LTE Interference on OTA Antenna TV
Replies: 16
Views: 439

Re: 4G LTE Interference on OTA Antenna TV

A 1/2 wave antenna for an AM broadcast station could more than 400 ft.

(is 2000ft an over estimate?)
by dyarker
Thu Jun 18, 2020 10:06 am
Forum: General Discussion
Topic: Voltage and Current
Replies: 4
Views: 156

Re: Voltage and Current

Electron flow, outside the source - electrons flow from the negative terminal through the external circuit to the positive terminal of the source. Inside the source the electrons are forced toward the negative terminal. The extra electrons at the negative terminal is what made it negative in the fir...
by dyarker
Wed Jun 17, 2020 5:11 am
Forum: General Discussion
Topic: Multisim simulation error in High-pass Filter Circuit Design
Replies: 2
Views: 90

Re: Multisim simulation error in High-pass Filter Circuit Design

Active filter? If yes, what cutoff/rolloff of the amplifier?

(images didn't work - had to ask)
by dyarker
Sat Jun 13, 2020 6:33 pm
Forum: General Discussion
Topic: 4G LTE Interference on OTA Antenna TV
Replies: 16
Views: 439

Re: 4G LTE Interference on OTA Antenna TV

But the tower i mentioned...the insulator was at the base of the tower, not the base of the antenna..
Yes, I got that the insulator was at the base of the tower.

That means the whole tower is the antenna. I thought bolding the word "is" in my previous would have been clear enough.
by dyarker
Fri Jun 12, 2020 10:46 pm
Forum: General Discussion
Topic: 4G LTE Interference on OTA Antenna TV
Replies: 16
Views: 439

Re: 4G LTE Interference on OTA Antenna TV

A tower on insulators is the antenna. There will be a spark gap at the base. Guy cables will have in-line insulators so that cable section lengths won't resonate at operating frequency.
by dyarker
Fri May 15, 2020 7:39 am
Forum: General Discussion
Topic: Superduper capacitor substitute for battery
Replies: 12
Views: 666

Re: Superduper capacitor substitute for battery

Super caps have a higher internal resistance than filter caps. That is lucky because you don't mention current limiting, and you didn't "blow" the LED. LEDs are not incandescent bulbs. With bulbs an increase in voltage increases current, bulb gets hotter which increases resistance which regulates th...
by dyarker
Mon May 11, 2020 8:23 pm
Forum: General Discussion
Topic: Superduper capacitor substitute for battery
Replies: 12
Views: 666

Re: Superduper capacitor substitute for battery

Thank you! (Wonder what I pushed on the calculator???)
by dyarker
Sun May 10, 2020 9:05 pm
Forum: General Discussion
Topic: Superduper capacitor substitute for battery
Replies: 12
Views: 666

Re: Superduper capacitor substitute for battery

It was indirect. He said he expected AAs to last 30 minutes. If it is rated 1300mAHr, that is 1.3A for 1 hour. So 2.6A for half an hour. (Though at high current loads you don't get the rated time.) A lot of LEDs, a LED headlight, or an incandescent does not matter for the question; "How much capacit...
by dyarker
Sat May 09, 2020 12:34 pm
Forum: General Discussion
Topic: Superduper capacitor substitute for battery
Replies: 12
Views: 666

Re: Superduper capacitor substitute for battery

Just spotted a 3500F super-super-cap.

One or two of those should do too.

(a question - is this an incandescent light? because the white LEDs I've seen need 3.8V)
by dyarker
Sat May 09, 2020 12:05 pm
Forum: General Discussion
Topic: Superduper capacitor substitute for battery
Replies: 12
Views: 666

Re: Superduper capacitor substitute for battery

Real rough. Found some nimh AAs that are 1300mAhr. So 30 minutes would 2.6A load (you won't get the rated amphours discharging them that quick) 1 RC time constant is 63% discharged. R = 2.5V / 2.6A = 0.96Ohms Time in seconds is 30min * 60S /min = 2160S T = RC so C = T/R C = 21605S / 0.96Ohms = 2250...
by dyarker
Wed May 06, 2020 8:30 pm
Forum: General Discussion
Topic: UVC Testing - Willing to pay!
Replies: 13
Views: 962

Re: UVC Testing - Willing to pay!

Had to go looking for what the "C" in "UVC" was for. It is shorter wavelength band than UVA and UVB. I agree that anyone selling UVA or UVB for sanitizing is cheating people and giving a false sense of safety. You, and anyone helping, be careful during your experiments. Living people should not in s...
by dyarker
Sun May 03, 2020 6:41 am
Forum: General Discussion
Topic: Question about a circuit again
Replies: 4
Views: 732

Re: Question about a circuit again

A voltage divider needs at least 2 resistors. Input at top lead of upper resistor and bottom lead of lower resistor. Output to measuring circuit is junction of the 2, and bottom lead of lower resistor.

If you are only going to AC with this circuit, then you won't need the DC divider.
by dyarker
Sun May 03, 2020 12:39 am
Forum: General Discussion
Topic: Question about a circuit again
Replies: 4
Views: 732

Re: Question about a circuit again

As far as I can tell the parts to the left of the ADC are the voltage divider. (and I don't see the 1.2K you mention in the posted diagram, nor figure 7 in the linked page.) C2 and C3 may be replaced with a single 30pF. Series caps are - Ctotal = 1 / ((1/C2) + (1/C3)) (30pF is not a standard value) ...