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Topics - vwflyer

Pages: [1] 2
1
I was reading this article about AGM batteries and noticed the graph relating to cycles and depth of discharge.

http://offgridham.com/2018/03/agm-batteries/?utm_source=amateur-radio-weekly&utm_medium=email&utm_campaign=newsletter

Now what I've always been told is that if a deep cycle battery is discharged bellow 50% you will significantly reduce it's life, ie reduce the number of available cycles. Most plans for how much battery capacity you need figures on discharging down to 50%. So if you calculate that you will need 100ah per day of storage you should buy at least 200ah worth of batteries. This will keep your batteries above that magic 50% number and significantly prolong the life of your batter.

Indeed, the graph does so a sharp change in direction right at that magic 50% mark. But after looking at it for a few minutes, it dawned on me that what the graph is showing is exactly opposite the above premise. To me at least, the graph seems to be saying that the first 50% of your battery is where the number of cycles takes the biggest hit and the second 50% has less impact on the number of cycles available to you.

So I crunched a few quick numbers taken from the graph. If I take a 100ah battery and drain it 50%, I get 50ah out of it per cycle and 700 cycles. 50ah x 700 cycles yields 35,000ah over the life of the battery.
If I only sip 30% off the top I get 30ah per cycle and 1600 cycles. 30 x 1600 is 48,000ah out of the battery during it's life. That's a whopping 52% increase in power harvested over the life of the battery.

On the other hand, if I discharge the battery to where there is only 10% left in it at the end of the day (I'm discharging it by 90%) it still gives me 400 cycles, not that many fewer than only taking 50%. In fact, 90ah x 400 cycles gives me 36,000ah over the life of the battery. That's more than I get when I discharge it down to only 50%.

So the graph is definitely showing that the first 50% of the power taken out of the battery takes the biggest tole on the battery's life. The shallower line means smaller changes in discharge result in larger changes in number of cycles and the steeper line bellow 50% means larger changes in DOD result in smaller changes in number of cycles. If you are going to pull it down to 50%, you are not losing anything to keep on pulling it down to 70%, 80% or even 90%. I wondered if this graph was wrong so I looked for more graphs online and they all say roughly the same thing.

Am I missing something or have I been misled all these years?

2
Antennas / Tuning the QRPGuys vertical tribander
« on: May 30, 2018, 10:34:44 PM »
Hey guys,
After reading many positive  comments here about the QRPGuys vertical tribander I decided to get one. It went together quickly and after a little adjustment got it working with very low SWR on 20 and 30 meters. I was using the built in SWR meter on my YouKits HB-1B. I know not the most accurate but it's what I have for QRP levels. Resonate on 40 meters was way to low so I wound up removing 2 wraps from the inductor and that got it up to where I need it. I was using just a short 3 foot coax jumper to connect to the rig. I decided to add 6 feet of coax to make sure it doesn't change anything. On 20 and 30 it didn't change much but on 40 it is now resonate way up in the voice part of the band with the extra length of coax attached. That is, unless I have my hand under the back of the rig, then the resonate freq comes back down to the CW part of the band. I'm thinking that I will probably operate this antenna with longer pieces of coax since I don't want to be tethered so close the the base of the antenna to operate. I can add a wrap or two back onto the toroid since I haven't yet snipped off the excess I had after taking two wraps off but that part of the wire is no longer insulated. What happens if uninsulated magnetic wire rests against the toroid? It will be fine as long as it doesn't come into contact with uninsulated wrap right next to it right? 

3
Morse Code / XXX
« on: May 20, 2018, 11:35:53 PM »
No, this post is not about Vin Diesel or adult movies. Rather, itís a question concerning the old practice of sending X X X in CW for Pan Pan, which is a call for assistance in non-life threatening situations. As a pilot Iím familiar with Pan Pan and I was curious if there was a way to call it in CW. So I googled it and discovered it was three xís sent as distinct letters. Iíve been messing around in CW for a few years now and never have come across this yet so it is not common knowledge like SOS is. I got to thinking about it as I was driving through a really isolated stretch of mountain roads last week, miles from cell service and thought that a way of getting the attention of a ham on the CW bands would be real handy if I had a breakdown and needed to have a ham relay a message for me to my wife to let her know about it and send some help if needed. I know SOS would bust a pileup and get a dozen of willing helpers in seconds. Do you think sending X X X would have any affect at all or am I better off just calling CQ HELP or something like that?

4
General Discussion / Lost at sea 5 months without comms
« on: October 28, 2017, 01:16:16 AM »
My curiosity is killing me and itís probably too early to get all my questions answered by the news. But I know that there are some sailors in this group so maybe there are some good theories among you. How did these two ladies wind up without comms at sea?  Iíve read several news stories looking for the answer. Several said their comms died shortly after losing the engine. Sounds to me like maybe the battery died because the generator was engine driven. Would that be right?  Do many sail boats not have solar power so that you donít have to run the engine to charge the battery? It is supposed to sail after all. Even so, would they not have made the distress call on the HF  before the battery died?  Is it possible they didnít have an HF radio on board? Are they not required on ocean going vessels? One article said they lost the sat phone overboard the first day out. Does having a sat phone on board qualify for comms requirements at sea and thatís why they didnít use HF?  Many articles stated that they made distress calls for 92 days but were too far out for anybody to hear them. From this I surmise that their VHF radio still worked. Perhaps an HT which is why it still had juice. If so that HT battery has good life. So many questions, Iím afraid Iíll have to wait for more interviews from them. Glad they made it. I imagine theyíll do a few things differently the next time out.

5
General Discussion / HB-1B Go Box
« on: November 24, 2016, 10:02:11 PM »
I wanted a bullet proof go box for my HB-1B. A way I could throw it into whatever car I was driving, or take camping, boating, traveling, or wherever. I wanted it to be small and transportable and have everything I need inside of the one box. The one-size fits all approach always ends in compromises and this is no exception. This is what I've finally gotten assembled.

Pelican 1150 case.
HB-1B
Sotabeams EFHW Tuner

Usually I have the AC charger in top space but when camping or for SOTA I can replace it with an external battery pack for more runtime off grid.

Under the tuner is a QRP Guys paddle, earbuds, 3ft of RG-174, power cable for external battery, small bungees.

Under the radio is 50ft of paracord, s-clips, EFHW linked wire for 20, 30, 40 meters.







6
General Discussion / NVIS or ground wave?
« on: October 03, 2016, 01:53:33 AM »
Big back story here.
I've started playing around with QRP NVIS to see what it's capable of. I set up my computer to auto start a recording of my home radio's audio at certain times. I then turn the radio on and tune it to the freq I want to try. I then go out into the mountains and set up my QRP rig and simply string my EFHW from tree to tree as high as I can reach. When I know the computer has started recording I call CQ. If someone answers great. If not no big deal, I just want to see if my home QTH recorded me and how strong I was. So far I've only made three attempts but plan on many more at different distances, on different bands, at different times of day and in different terrain. The first attempt was at 130 miles on 40 meters in the mountains at 9:00 AM. My recording heard absolutely nothing. Then it occurred to me that my noise floor on 40 at my home QTH is always S7 or more. That could be why I didn't hear anything. If my signal was S5 it would have been buried in the noise. So I decided to try 30 meters out as it's a lot quieter than 40 at home. On the second attempt  my recording never started for some reason so who knows.

On my third attempt I was just going to a friend's house in town about 12 miles away from me. He has a big yard so I figured I'd take the little rig along and try a 30 meter contact from there. Long story not so short, my recording picked up my CQ quite well at 12 miles on 30 meters at 3 PM.

So here's my question. Was I using NVIS or ground wave to reach home? Both of our houses are in low spots so while there are no big hills between us there is also no chance of line of sight communications. My 2 meter FM base station at my home can't get more than about 8 miles towards town when talking simplex with my mobile rig and both are running 50 watts, not 4 watts that my QRP rig runs. The antenna was oriented for NVIS and not ground wave but at 12 miles it might not matter. Any opinions?

7
Radio Reviews, Questions and Comments. / QYT KT8900 Dual Band 25W Mobile
« on: August 13, 2016, 07:07:47 PM »
I just came across this rig. I've never seen it before but you can't beat the price for a duel band mobile. Has anybody heard anything good or bad about these radios? I don't see where in the specs it mentions receive current draw but it's small enough to be a decent go box radio with more power than a handi talki.

http://www.banggood.com/QYT-KT8900-136-174400-480MHz-Dual-Band-25W-Mobile-Radio-Transceiver-Walkie-Talkie-p-1026663.html?currency=USD&createTmp=1&value_ids%5B%5D=29&utm_source=google&utm_medium=cpc&utm_campaign=Crc-dm-c7&utm_content=ruby&gclid=CJ3q9r_0vs4CFQouaQodwZYGCA

8
Antennas / Magnetic loop to cut the noise?
« on: February 12, 2016, 06:14:36 PM »
For a while now my brother and I have been trying to set up a sked. We are still struggling to find a band and time that is reliable. Part of the problem is the noise level he has to deal with at his QTH. He lives in the Seattle area and has to deal with a constant noise level of s6 and up on all bands. I can often hear him fine but I'm down below his noise level. He is currently using a G5RV installed stealthily in his backyard. He lives in a HOA and can't put up an obvious beam.

We have been researching magnetic loop antennas for their high Q and noise rejecting characteristics. I know some of you here have experience with them so I was hoping you could give me some insight into them. Do you think that they are a viable option for this situation?

9
General Discussion / 1,600 mile sked
« on: October 23, 2015, 07:25:32 PM »
Well, my brother finally got his General license. He lives in the Pacific NW and I live in the South, about 1,600 miles apart. He plans on bugging in so he has a solar generator and a 100w HF rig. He lives in an HOA so has to have a stealth antenna. He is starting out by trying a G5RV inverted-V in his back yard. The feed-point is at his house peak and it slopes down to the top of his fences in the back where it runs along the top of the fence for a bit. The ladder line is running horizontally through his attic. He lives on a corner lot so it isn't really visible to people within the HOA.

I have a OCF 80 meter dipole inverted-V with the apex at about 30ft. Both of these probably make fine NVIS antennas but aren't the best for DX. We have been experimenting with setting up a sked between us but so far have not found a time or band that has made SSB viable with our situation. I've been telling him he now needs to learn morse but I can't rush him. He has heard me sending CW on several occasions but he can't respond or understand.

Finally I told him to download a PSK31 program for his phone and just hold it up to the radio's speaker while I send. It decodes my PSK31 just fine. He held the radio's microphone to the iPhone's speaker and sent me PSK31 and it works as well. So now I'm helping him build an interface that will go between the iPhone and the radio to make it even more reliable. He can easily keep his phone charged with the solar generator. This seems like the best solution until he learns morse code and even then I have found at times that PSK31 can be decoded at lower levels than I can copy CW. In fact, when my brother sent PSK31 to me using his iPhone and microphone I could just barely hear the signal coming out of my radio but the computer decoded it just fine. Had it been CW that far down into the noise I would not have been able to copy it at all.

We are not about to buy amps to help us out. I would some day like to put a DX antenna on my roof like a hex-beam or spider-beam or something and point it right at him but that will wait till I have more money. With his HOA, he doesn't have that option. I was impressed with Ray's magnetic loop when I spoke with him the other day. I wonder if one of those would help him pull my signals out of the mud.

Several of my co-workers are down in Tepic, Mexico right now and are expecting the hurricane to hit them any time now.  I would be there myself right now but my coworker went in my stead since today is my oldest's 15th birthday which I didn't want to be gone for. They are stocking up on supplies and taping the windows but none of them are hams and don't have a radio to fall back on if they lose cel phone and internet. They do have a Spot tracker and a sat. phone though so I'm sure they'll be fine in the comms area but I still wish they had an HF rig with them. They are coordinating with local authorities to start relief flights right after the storm passes. There is no ARES equivalent in Mexico. If there were I'd probably be a part of it. It would sure help us coordinate our flights when commercial comms go down.

10
Technical Corner / BangGood QRP tuner
« on: October 23, 2015, 04:04:40 PM »
Hi guys,
Does anybody have experience with this inexpensive tuner? I have ordered a few kits and things from this outfit before and so far I've been pleased with what I've gotten but I figured I'd ask first.
http://www.banggood.com/QRP-1-30-Mhz-Manual-Antenna-Tuner-Tune-Kit-p-914663.html

11
General Discussion / QRP Works!
« on: May 19, 2015, 11:23:46 PM »
At least it did last weekend. On Saturday I got out my new MTR to try out the linked EFHW I just built for it. I also took the opportunity to save a CQ to the radio's keyer memory. I was experimenting with using the beacon mode where it would continue to send CQ until I stopped it but I was having trouble testing it because someone would come back to me at the end of the first CQ every time I tried it. I almost never get that kind of success on my QRO rig and permanent dipole. I don't know if it was luck or good propagation conditions or the fact that the memory keyer has a better fist than I do so people are more willing to answer (my QRO rig doesn't have a memory keyer). Whatever the reason, it has made me a belever in portable QRP. It gives me some hope that I'll actually successfully activate some summits this summer. I just hope that it doesn't work too well and I wind up having to deal with a pileup. I'm still green when it comes to morse code so I don't know if I could handle multiple summit chaser call signs coming at me at all at once.

12
Radio Reviews, Questions and Comments. / Next QRP CW Rig?
« on: April 22, 2015, 02:01:39 AM »
The rockmite is really fun. Every QSO with it is exciting. The other day I tried to have a QSO with KK0G but the rock's freq was in use and stayed in use for a long time. It would have been nice to have the option of moving up or down the band a little to a clear spot. I did eventually make a contact that day but not with KK0G. This summer I will be going to my home state of Washington. I hope to try being an activator of summits with SOTA. there is a four point summit that has not been activated yet and I will be staying with my in laws who live halfway up the hill. It will take me 20 minutes to hike to the top from the door of the house. There are lots of 6 and 8 point summits within a half hour drive radius so I will enjoy having an excuse to hike up some of them that I have seen all my life but never hiked up. 
All this to say, I'm already anxious to get another QRP rig. One that is a little more flexible than the rockmite and will give me a better chance of having successful activations (4 QSOs minimum for summit activation). So which to get?
I'm into building them but don't know if I'll have time to do it before this June when I leave. I'm sure I will eventually build something but probably not before this winter. In the meantime I want to buy something ready to go for this summer.
LNR has the mountain topper prefabbed. It's supper small and has low power consumption. Youkits HB1A and EK1A are cheaper, have a real tuning knob, a wide range receiver and veriable width IF filter for listening to SSB QSOs anywhere on the band, and an optional internal battery. It's a bit bigger and heavier but that's about the only downside I can see. Does anyone have any words of wisdom for me? Is there another option that is in this $250 ballpark that I'm going to kick myself for overlooking?  I've actually already ordered the mountain topper (grabbed one before the limited run ran out) but they take a long time in processing the order so after looking at the youkits I'm tempted to cancel my order and get one of those.

13
Technical Corner / Repurpose HF gear
« on: December 31, 2014, 02:42:01 AM »
Happy New Years eve gang. Since you all have your thinking caps on from PuJo's question I figured I'd slip one in myself. About 3 years ago the mission I fly for decommissioned all of its HF stations. We used to use them to keep in touch with the missionaries living in the mountains of Mexico. We had a morning sked with them and they'd let us know that they were all right and if they needed supplies flown to them or if the plane needed to go out there for some other reason. After all of them got satilite Internet and determined it was reliable enough the mission finally decided to quite paying for the use of one of the mexican commercial HF freqs and the radios were taken out of service. They have let me do what I will with the radios. They are simple single channel 100 watt radios that are currently crystaled just below the 80 meter band.

So, what do I do with them? Is there a market for single channel radios like these? I thought they could make nice digital stations for a preppers digital network. I'd have to re-crystal them and figure out how to turn down the power. I doubt they can handle digital duty cycle at 100 watts.




14
Technical Corner / Yet another RockMite thread
« on: August 19, 2014, 09:41:35 PM »
My 20 meter RockMite has arrived! This will be my first transceiver kit. I'd been talking to my wife about getting one for some time and I finally ordered one without telling her. It came pretty quickly. When she saw that I had gotten it she said that she was planning on buying it for me for my birthday. Now she says I can't build it until after my birthday which doesn't come along until the end of November. We shall see who will win this one.  ::)
I ordered it with the $10 accessory kit which comes with two pots for volume and keyer speed controls, transistor for increased power output, heat sink, on/off switch, power indicator LED, and a bunch of resistors (one for the LED and one for the power mod, not sure what the others are for). The funny thing is that the optional transistor has identical markings to the one that came with the stock RockMite. I think that both transistors are the more power ones. The stock kit also came with a heat sink and green LED so I'm not sure why the accessory kit duplicated those.
This RockMite also came with a ten pin SIP socket and short crystals. I'm assuming I'm supposed to cut the SIP socket into three pin sockets and put the crystals in them but the instructions aren't explicit about it. They probably just assume I know that I can cut the socket to the desired length and don't have to tell me to do it. It will be nice to be able to easily switch between 14,050 and 14,060 though.

15
Morse Code / CW gets a nod from Fox News
« on: May 19, 2014, 10:54:54 PM »
At the date of this posting this story can be found on Fox's front page on the web.

http://www.foxnews.com/tech/2014/05/19/ham-radio-old-technology-gets-new-respect/?intcmp=features

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