How To Calculate Wire Antenna Length

We're talking Antenna Wire Length Calculations, Yaesu 891 V Icom 705, and Tarheel Antennas for HOA's!
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[@camrodger8638]

You handled the first question graciously and in a mature fashion. Much respect to you. Thanks for another great video.

[@hamradiotube]

My pleasure!

[@Matthew-KN4QHQ]

I started with an 891 that shared shack and field use. I made a speaker wire dipole that I used in an inverted V and only worked 20 portable. I do not regret it at all. This radio taught me a lot about working HF. It has also set the foundation for future radio purchases. I would go with the FT-891.

[@keithhawkins4641]

I would recommend the 891 as first radio. If you want low power dial it down. Sometimes new folks get a little frustrated when no one answers back and you start looking for troubles that are not there!

[@DARTHDANSAN]

I’ve had mine for year with man pack whip antenna. I can hear me people but no one has every seemed to here me . I gave up . All this money spent and I never make any contacts ✅✅🥹

[@DuhBiggestDog]

With regard to the Tarheel question.....I used a Tarheel with my 40' 5th wheel camper for many years. It is well built and never failed me. I also used a memory controller with it which made jumping from band to band easy. The Tarheel was mounted atop fiberglass poles, about 30' up, attached to the ladder on the back of the camper. I used 2 40M 1/4 wave linked radials with it and it worked great. The key, as it is for all verticals is an effective counterpoise system. 73 - Don K2PMC

[@KN4RAY]

I have both. QRP is fun but not for everyone. FT-891 if a great radio to start with.

[@F4LDT-Alain]

Interesting and informative video, thanks. Hearing a US citizen say "we should use metric" always is nice 😁 As for the transceiver question, I'd say go Xiegu G90. I have both a FT-891 and a G90 and I hardly ever use the Yaesu when working portable, which for me is 90% of the time. With a proper antenna as you mentioned, 20W is enough to make it through the pileups. And this radio is great: it's sturdy, power efficient, I always get praise for the quality of my audio (using the bundled microphone). And once you've tasted a radio with a waterfall display, it's hard to live without it IMHO. (yes it's tiny on the G90, but quite usable).

[@leestanphill1]

love the item on the cart in the background.. can't ever have too many G's

[@hamradiotube]

Ha! That's my newest toy. Had to get the G43X MOS.

[@mindfulmunchkin1215]

I'e done more with my new ft891 in 1 month than I have with my 705 in two years. Great radio great power.

[@jamesabc372]

705 is probably ok ,for CW.

[@peterdekeles.]

891 then 705. Great Monday mailbag. Hope those quesadillias were good.

[@Martin_Lynch]

Always good honest advice and interesting topics.

[@hamradiotube]

Thank you so much!

[@w4id676]

I've had my ATAS 120 antenna in the attic using a faraday cloth as a ground plane. It tuned on all bands except on 10m.

[@humbertocartayajr.5230]

How big of a mesh cloth did you use?

[@w4id676]

@@humbertocartayajr.5230 It is 108" x 43". There are several KZbin videos using faraday cloth with vertical antennas. The results have been good.

[@humbertocartayajr.5230]

@@w4id676thanks, mine was considerably smaller than that, probably why it didn’t work. Will try getting a bigger one. Thanks

[@Screamingtut]

Mike, it would help if you also told them about the federal law that states that HOA's cannot stop them from putting up antennas.

[@Retired_Five-0_W4WAG]

I thought that was recently proposed but wasn’t passed yet. If I did and I missed it, that’s awesome!

[@chrisnmichelle0218]

It gets proposed every few years, it's a bill, but probably won't ever be law. I track those bills every time hoping it will finally pass, but not yet

[@hamradiotube]

I wish that were true.

[@1shARyn3]

One problem on the EFHW --- your derived measurement in metric didn't include the VF (the imperial uses 95% for VF), so the metric is already a smidge long and ready to trim

[@Clark-N1NVK]

I live in NM... I use the 891... set to 80w in the car, with Hamsticks... and set to 50w when portable with a 17' on a tripod for POTA. I have over 1000 contacts on POTA. ... I have tried QRP, I want the power !

[@tmccusk1]

Strong work tonight Mike. Thanks for going over the antenna length. 73 KB1LQX

[@DonDegidio]

Hi Mike, Wish I didn't need to sell my 891 and ATAS. Miss it already. Just sold my MFJ ALS-606S for less than half what I paid. Had it up for sale on QTH, QRZ, and Josh's Discord for about a month with no takers. Had to settle for an offer from Maine Trading Company. May also need to sell my FTdx10 which would put me off the air until my financial situation takes a turn for the better. Stay safe. 73 WJ3U

[@Dazdigo]

Just say the equation is just the speed of light divided by the frequency then multiply the fraction of the wavelength you wish to use. If you want to convert it to imperial, then multiply it by 100 (cm in meter) divided by 2.54 (cm in an inch) to get the length in inches. As a math major, I like everything exact. Much easier to remember than random constants which you don't know where it came from.

[@robmccray6360]

Every Ham should own at least one meter-based tape measure.

[@paulsengupta971]

In the UK, all our take measures have both centimetres and inches on them. I just thought that's how tape measures were until I saw a US ham video where he brought out a tape measure and it was only in inches. I was a bit surprised.

[@dorvinion]

@@paulsengupta971 Ya'll kinda use both to some extent for length measurements right? Aside from people who need do so because their profession uses metric, we don't use it for anything period so there basically no reason to measure anything in metric units so putting both on a tape is kind of pointless What we often have instead is a fine scale on one side and a course scale on the other The tape measure I have in my office has a 1/16 scale on one edge and a 1/32nd scale on the other Not too unusual to see 1/8th on one and 1/16 on the other, especially in building trades

[@davenewmyer3735]

I have the 891 & Nifty1 mini manual. Really helps for those menus. Hope you are finding time for a little cw. 73 de n0km

[@slick8086]

I got the 705, I'm getting the Hardrock 50 amp whenever they ship it out.

[@stahpit1971]

Good info as always

[@Aloysius-73]

You can use the jaw clamp mount on the railing or umbrella stand for the Tarheel. Chameleon or Amazon has them.

[@BlessedLaymanNC]

891 vs 705... I have used the 857 for years. It is heavy to lug around and the receive current can be reduced to below 1 amp. But, when needed, I could raise the power. On battery, with the connector I had, it would do a maximum of 50 watts, but I tuned the minimum powers down to 1 - 2 watts. I don't know the weight of the 891 that uses a similar case, but my friend who has one says he can only minimize the current draw to 1 amp on receive. I don't know about the minimum TX power, though. I'm sure it not higher than 5 watts. I don't know what power supply the person making the choice has, but current draw is important if it is on a battery and size depends on how long he wants to operate. The 705 is QRP only and QRP builds a different skill set from higher powered rigs. If this is a first rig, there are a few things I learned from starting off with a reduced powered radio, not necessarily QRP. Being part of a rag-chew group on 75 meters at night and early morning pretty much requires more than QRP because of the noise floor. The same often holds true on 40 meters but 40 meters is a little more accomodating at times. It is a great QRP CW band most of the time. Above 40M, the bands are more suitable for QRP. If a DX station is a little weak, QRP can be really tough to get through. But, if its strong enough, your call/QRP will often get you a priority response. Battery power will determine how long you can operate. My friend with an 891 says he cannot reduce the current draw under 1 amp in receive. The spec sheet says the 705 draws .5-.8 amps depending on the battery voltage. I think the 891 can operate down to 9v, but the 705 goes to 7.5v. The higher voltage gives a higher output. A big enough battery or power supply overcomes all of this. QRP is a lot of fun, and has a lot of frustration. When I operate QRP on my higher powered rigs, I have found it necessary to raise my rig to full power to tell some lid to QSY who pretends not to hear my "weak' signal. If the incoming signal is strong, then you can be heard. Some hams are dedicated QRP fans. Some QRPers have convinced themselves that operating above QRP is illegal. Regardless of power, use the best antenna you can possibly use wherever you are. If you are the kind of person who has lots of patience and love challenges, you may be more suitable for starting off with QRP, if not, go with the higher powered radio, a bigger battery and operate on the lowest power you can get away with while you learn the skills to operate QRP. There is plenty of room in Ham radio for QRP5, QRP10, QRP20, QRO1500 and anything in between. Pick your game and play. 72/73

[@KeepEvery1Guessing]

(The reason that all those antenna formulas came out in feet is that the tape measure in your dad's toolbox was in feet.) But note that the two calculations aren't going to agree. 300m/usec is a good FREE SPACE value for the speed of light. 300m/2 in feet is 492.126. The 468 number comes of trying to compensate for velocity factor (and maybe end effect) in aluminum tube beam elements, and may be a bit low for wire elements. Yes, wire has a velocity factor, and it depends on wire diameter and on what kind of insulation, if any, is on the wire. You will definitely want to cut long and trim if using 468. I believe that I have seen 487, but that's' a stray memory, rather than something I've looked up (I think it was for copperweld).

[@Davidjb37721]

Thanks for your help 😊

[@willian.direction6740]

My ft891 is a great portable radio I only put into memory the "usual" parks frequencies and that way its easier to get going out portable and put in Spots on the web pages. But of course if the frequency is in use I find a clear one. Run rig at 30w on SSB and 20w on CW also set in the menu. KX3 is 8w for SOTA, good thing about lower power and these activities is most Chasers/Hunters of Parks or SOTA have found you from the Spotting pages and expect your portable signal to be a bit lower than a big gun home station. But sometimes my portable station is as strong as some 100w home stations any how because I use resonant antennas on each band.

[@fthorup]

YES YES YES - of course we use metric. YES you said it!

[@EmJayArr]

"Ham Shit" folder 😆

[@hamradiotube]

That's not just for ham. Every folder is something Shit.

[@johndextersantos9541]

at 4:25 i keep closing the calculator app on my screen and it kept pausing the video, , , it was part of the video LOL. . . I was not looking at the screen the whole time, just listening 🤣

[@DarkShadowCustoms]

I think part of why we prefer imperial measurements such as feet in the US is because it is much easier to find a foot tape measure than it is to find a metric tape measure. I agree that it is hard to bust a pile up when using lower powered radios. I have a Xiegu G90 that shares shack and field use. It is difficult to bust through pileups with 20 watts. Not much issue calling CQ when the bands are cooperating. The G90 was a gift from my Elmer when I passed my General exam last year. I wouldn't mind having a 100 watt radio for home shack use and keeping the G90 for field work. I got a laugh from the ham wanting to smack the HOA president with a Tarheel antenna. I am glad I live out in the middle of farm fields and don't have to worry about HOA restrictions.

[@anthonymassey4222]

For the first HF radio I would suggest the 891 mainly for the 100 watts. I feel a QRP such as the 705 or one of the others wouldn’t be as good for what his said use is expected to be and would only cause frustration

[@KS0JD]

What is this calculator you speak of? Will it replace my trusty slide rule? Hi Hi Thanks for the video! 73

[@hamradiotube]

Hahaha!

[@W4EMB]

Mike, Thanks for the videos. I have always referred to SH-2176 for my antennas. (its a handbook from my previous life)... 234 divide by freq ... That will get you in the ball park for 1/4 wave. Double it for 1/2 wave ect. Of course add a few inches.... I use Freedom units ..then trim to freq.. Thanks Mike

[@VE3FAL1Fred]

234 for me as well for 1/4 antennas. 1005/freq for full wave loops.

[@russellyeley2561]

My brain is old and full. Have had my tech and general for about 6 months. I have to go back and look at the books because I don't remember everything.

[@RobB_VK6ES]

I would advise against the mobile antennas for fixed installations, their efficiency is woeful not to mention they are expensive. A 1/4 wave vertical (which the shortened mobile antenna is emulating) has max current at the feed point and would require a substantial ground plane. It is the current which determines the radiation. Since the mobile whip has mostly loading coil near the feedpoint, the vast majority of the rf current is confined to the coil which is not good. IMHO a 1/2 wave endfed draped from a standoff pole will give much better results from an elevated balcony

[@Philip-KA4KOE]

I use 22 awg UL1007 wire. Works out to 0.98 Vf. Insulated wire always is too long. Someone gave me a bunch of 15 KV neon sign wire. I made a dual band vee. On 75m, I had to lop 4' off each end. 891.

[@billybunter230]

Hi Folks. I'm new to all of this stuff, so I am going to ask the most stupid question. I have a Yupiteru MVT 7100. Is it possible to build a 1/4 wave antenna if I calculate the frequencies and lengths of the wire. Or are these aerials only for ham radio.

[@hamradiotube]

I'm not sure what radio you're talking about but an antenna is an antenna. It doesn't matter what you're using it for, so long as you make it resonant on the frequencies you plan to operate. These calculations will work with any antenna for anything that needs an antenna. You could make a TV antenna if you wanted.

[@DanyPelletier]

Doing calculations in meters with the (300) never gives the same result as doing it in feet with (468). With your example, using a frequency of 14.175, the meter calculation is about 9" shorter. I'm guessing that it does not really matter because it gets you close enough. But does it mean that you could end up to short on the meter side.

[@SwissAdventureRider]

But you're not accounting for the speed of electricity transmission into the wire so you still have to multiply by 0.95 (Avg)

[@TinyTJ04]

Came for the old school calculator spelling joke and stayed to find out if the Tarheel could take down the HOA.

[@hamradiotube]

Finally somebody got it!!

[@TinyTJ04]

@@hamradiotube that was a blast from the past, AND a service to the community. Kids should know this stuff. :)

[@Eric10179]

I always thought it hilariously ironic that of all the countries in the world, America still uses the old Red-Coat measuring system 😂

[@kimparkin5254]

Velocity Factor of the wire?????

[@hamradiotube]

Is variable. As we learned in our amateur radio text books, these are rough formulas to get you in the ballpark.

[@FosterFarmsOk]

I left my metric tape measure in the UK 240 years ago

[@paulsengupta971]

I found it and gave it to a museum.

[@hamradiotube]

🤣

[@deltaqnord3103]

300÷14,175=21,16÷2=10,58×0,95=10,05 meters😋

[@alvarogaitan2529]

jejjejjje Albert Einstein is sooooo funny jejejejjej thanks sr genius

[@KO4GBB-Moe]

891

[@ronw1vet]

I don't cut the wire I fold it back on itself as long as it is not more then 2 feet.

[@Toner-N1SWT]

I own both radios and I like the Icom 705 better. It's an all in one radio with an outstanding menu in the radio. Has bluetooth and wifi connectivity which makes FT-8 a breeze. Also use it for vhf communications. My go to radio for sure.

[@stephanhersey1186]

891 Half the price of the 705. Enough said for me. Steve, k7ofg

[@charlescaudill2651]

I guess I used feet making mine because I don't have a tape measure in metric yet

[@hamradiotube]

Come on a 100' dual metric/imperial spool is like $12 at Harbor Freight. That's what I use.

[@charlescaudill2651]

@@hamradiotube lol yeah I know... I just keep forgetting to buy one every time I go! Need to write it down....

[@daveengstrom9250]

I prefer 300/f THEN do the Google conversion: Meters to feet. Simple.

[@NolanRollo]

As an American with access to a metric tape measure, I never understood why all Americans demand to build antennas in feet.

[@dorvinion]

Because almost everybody in the US already has one or more imperial tape measures and accurate converting between the units is trivial. Aside from cutting antennas I can't think of any other reason to have one so its basically a single purpose tool. Why buy a single purpose tool when you already have an effective substitute?

[@hammathguy3995]

Why 300/f and then half that? Why not just 150/f and be done with it? And, as others have pointed out, the metric solution gives the full length of a half wave. 468/f solution is about 95% of a full half wave. Use 492/f if you want a full half wave length.

[@dandypoint]

For most wire antennas you want to apply the proper velocity factor. That 95% is an estimate to get you close. Height above ground, wire size, insulation and insulators are major factors so trimming may be necessary.

[@paulsengupta971]

Because you 're starting from first principals. 300 is the speed of light in metres per second x1m. The formula is to work out the wavelength from the frequency, where you divide the speed of light by the frequency to get the wavelength. So 300/14 (with six zeros on each) gives you the wavelength of 14MHz in metres.

[@hamradiotube]

That's assuming all wire has a 95% VF. As the textbooks teach us when we are studying for our exams, these formulas are not exact, but get us close enough. Then we cut them long, which totally throws everything out the window. Sometimes good enough is good enough. Don't over think it.

[@donaldsmith3048]

There are people that use metric, and there are people that sent men to the moon! I have a question. When all my measuring tapes are in imperial, and I must change to that to be able to cut the wire. Why not just start out using feet? That is what you measure tapes in! I hope to find a measuring tape in metric that I can get but at this time it is easier to just do everything in feet! I know it is a problem for some but with my work, doing things in feet is easy for my old brain! HAHA! 73 W4DES

[@hamradiotube]

It's $13 Don. You can focus on the problem, or you can focus on the solution. The choice is yours. www.harborfreight.com/100-ft-x-12-in-open-reel-measuring-tape-62411.html

[@F16_viper_pilot]

So why is it that when you take 10.58201 meters and convert to feet you get 34.71788 feet instead of 33.01587 feet? One of these formulas is not correct.

[@dandypoint]

He did not apply the velocity to the 300/f formula after he got a full wave in space. 468 has had a velocity factor applied already.

[@F16_viper_pilot]

@@dandypointMakes sense, but I would argue that velocity is not a constant. So people need to be aware that no antenna length can be calculated with a formula that does not take velocity into account as a variable. Thus even the 468/f is only an estimate, based on a specific velocity.

[@dandypoint]

@@F16_viper_pilot no argument there! I said in my comments somewhere on this video that it was an estimate and varied with many things such as size of wire, insulation, height above ground and even then number of halfwaves in the wire! For all practical purposes using 468/f gets you close enough that maybe you don’t have to trim too much. I find that has always given me a longer length than I need. Sometimes it is good enough that I can just use it, most likely I have to trim once. When I check resonance very near the ground the antenna appears long and when I raise it to 30 or 40 feet the resonant point increases. I once had an 80 meter center fed conventional inverted Vee. I could change the minimum SWR point from CW to SSB bands by raising and lowering the ends. In any case you get different length when using no velocity factor or using 95%. Regardless the video did not use a velocity when talking meters but did use a 95% when talking feet. Someone wondered why there was a difference in length when he converted meters to feet. That’s why. So I think we agree 100%.

[@8TangoCharlie]

VF (Velocity Factor)

[@F16_viper_pilot]

@@8TangoCharlie Velocity factor has to apply regardless of units. It’s not like you apply it only when working in one set of units and not the other.

[@ke8wlw]

Kitty

[@x_CrossHair_x]

300,000,000 Meters per Second (Easy to Remember) .. But a More accurate Value would be.. 299,792,458 Meters per Second and for some more FYI (Velocity Factor of Copper Wire is: .98)