• Announcements

    • Zapata

      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  


  • Content count

  • Joined

  • Last visited

Community Reputation

2 Neutral

About Jaramaz

  • Rank

Profile Information

  • Location

Recent Profile Visitors

1,353 profile views
  1. Jerry, don't be so hard on yourself. You are so agressive - why? We have to clear some things here: Dynamic range of a mobile phone is not really the most important factor wrt its radio range. Instead reciever sensitivity in downlink and output power and PA linearity in uplink are the important factors. Coming to the first link you offered, the one from ADI, that was about radio base stations. The paper discusses necessary dynamic range for the reciever in a base station, not the GSM System dynamic range (system dynamic range is not the same as receiver DR). The paper use a 12 ADC as an example - that was what was used in base stations at that time with the architecture used. A 12 bit ADC gives about 75 dB dynamic range (probably drops some 4-6 dB as enob is likely to be ~11 ), to improve reciever DR further one adds AGC and in the paper it is suggested to go for oversampling to supress noise which further improves DR. In 1995 that was what one could do, nearly state of the art. A mobile phone does not have the same requirements; a base station is a multi user system whereas a mobile is a single user. Radio and baseband architecture is quite different for base stations and mobiles: A base station must be able to handle many simultanous mobiles near and far, to handle blockers, interference etc whereas the mobile will be assigned a frequency which isn't full of interferers. A mobile simply doesn't demand such high DR, and to in 1995 put a 12 bit ADC in a mobile - no, that would be too powerhungry, too large footprint and too expensive. The paper of the second link you offered is very general. Doesn't say anything about application it is just about how it is possible to design a high performance reciever - figures are reasonable and generally ok, even if the architecture it is based on is somewhat dated. Of course it is possible to achive very high DR - if you can afford it in terms of power consumption, cost and size. Which you can't in a mobile. Lately it has been discussed to use real low resolution ADC in eg 5G due to the high isolation in those systems. As 3-4 bits ... something for you to consider . Myself, I am not so sure this will be the case in products, but you can easily find both papers and patents on this. The argument " my last 2 boats were largely paid for from contracts working for Motorola, Broadcom and Qualcomm I got a different story to tell. " is a rather weak one. You are not saying anything about what you really did in this work; very few, if any, is designing a complete mobile by themselves. There use to be different teams - rf, baseband, audio and so on. //J
  2. Dear Paul, You have not really understood the charm of an anchorage which offers a full nights sleep (or whatever). Denmark has about none such outside their horbours (OK, I know about some very few places), compare that with Swedish west coast which has some few hundreds or the Swedish east coast which has about infinite amount of completely safe and good anchorages. Similar in Finland, there are endless possibilities to just drop the hook, fix your dinner and go to bed. Then in the morning , start with a nice drop and a breakfast while the wind builds up. This does not exist in Denmark (or Germany). Been there, done that. //J
  3. Commonwealth Games (or Australia Games)

    Agree on that. However, Sweden has neighbours: The pic was posted by "Finnfish". if that may be a clue. //J
  4. Longitudinal Rudder movement

    Suggest a look at the Jefa webb page: http://www.jefa.com/ they have method and solutions for non-round shafts. Having said that, when I dropped my rudder some few years ago I noticed my shaft was not really round / circular (plastic bearings, ss shaft). I polished a bit, most probably with little or no effect, and re-mounted with a new plastic bearing (non Vesconite, btw, based on some research.). Worked fine, better than I hoped for. Agree that 0.001 is not to worry about, can you even measure it? (depends on what unit you are referring to). //J
  5. Addendum: Most operators publish coverage maps. Easy to find and understand. Use to be somewhat exaggerated. For KPN there is https://opensignal.com/networks/netherlands/kpn-dekking or KPN itself http://www.kpn-international.com/network (but then you have to use flah, which I refuse). //J
  6. For sailing in Finland and Sweden a cat works fine, there are many natural harbours (no service,, no fee) where a cat is nearly ideal (limited draft, can tie to nearly any rock). Denmark and Norway has about no archipelago, thus one has to visit the harbours / marinas and then a cat is problematic (to put it mildly). In particular as large as > 45 ft! 5 months in the Scandinavian waters is a stretch. Doable, but limited fun. Water is very cold in the early season (until June), nights are getting dark in end August / Sept and weather detoriates quickly in the early fall. //J
  7. Longitudinal Rudder movement

    Bearing bronze should be somewhat oily when you touch it. One would guess that bearing bronze has been used but with boat builders you never know. The bronze bearings are often thinner (thinner walls) than those made of plastic - otherwize I would recommend plastic (some UHDM or even more advanced) but that would probably require a new ss tube. Congrats to the bearing removal, btw. It is always good to do such operations as one learns a lot on how the boat is built. //J
  8. Yamaha 4hp 2 stroke

    Did that on such a one from early 1980-ies. There are some screws - if you have the manual then you have removed all (?). and then the gear handle. Actually, I had no problems at all with that part - but the lower part, the gearbox, that was not nice. When re-assembling and running it I realised that it is much more quiet now, maybe I had a leak in the exhaust part. There is a gasket at the bottom, it is tempting to use some kind of liquid gasket on that part which also works fine as a glue. Suggest some (careful) heat. //J
  9. This thread is somewhat confused: the subject is said to be GSM but all posts is about later generations. And then there is talk about frequencies, LoS, dynamic range of mobile phones ... GSM in its original shape was had a very robust modulation, gmsk, was based on time slots and frequency separated up- and downlinks, ie TDMA/FDMA/FDD, with an associated bandwidth of 200 kHz. Very robust al of it. The time division slots resulted in a maximum of 34 km between mobile and base; the original mobiles had a max output power of 6 W (car mounted). The standard has been upgraded in many steps, GPRS and EDGE has been introduced to increase data rate as well as using double adjacent time slots to increase radio range - with that it is possible to reach up 200 km. If the base and mobile power amplifiers are strong enough this is certainly possible . However, there is little or no market demand for these radio ranges, and a modern smart phone output power is < 1 W. The traditional fequency band for GSM is 900 MHz, in the early 1990 also the 1800 MHz band were added. Higher frequencies generally gives shorter radio range, which also higher modulation, as used in EDGE does. Moving on to 3G, CDMA technology (in Europe the WCDMA with 5 MHz bandwidth), the users are separated by code and not so much by frequency and time. 3G was motivated by data rate, and certainly not radio range - in almost all cases 3G radio range is shorter than GSM. For 3G there is the same story about improving standard, introducing HSDPA and similar ideas which boosted data rate but also was a priority put on the users close to the base - we got cell breathing resulting in lower data rates at the cell edge and lower prio for users with a lousy link budget. 4G, LTE, is OFDMA based. To some extent going back to the basic principles of GSM. Again, the driver is data rate, LTE is now capable of delivering up to 1 Gbit/s user data rate - close to the base station (LTE advanced). As in the first approx data rate is proportional to output power (Shannon) then radio range has to be limited, combined with the fact that modern smart phones spend a considerable power to feed the display so from battery budget point of view there is not much left to use for the rf output power. In real life - be happy if you get more than some few km radio range. Specialized solutions are possible to get better range. Spectrum (in Europe) is now mainly said to be technology neutral, resulting in LTE using frequency bands from 700 MHz (from the digital dividend) to 3.5 GHz. In some countries LTE has inherited the 450 MHZ from 1G (typically NMT), narrow band but gives good coverage. Finally, no there is not any cell phone which can handles recieve signals with a dynamic range of 100 dB. Ability to handle dynamic range in any signal is given by the (rf) A/D converter, which typically has 6-8 bits resolution in the best recievers. The reciever sensitivity of mobile phones has improved very much over the years, somwwhat hampered by the increased bandwidth. To set up a call / connection some signalling in both downlink and uplink must take place, thus it is not sufficient for the mobile phone to recieve signals it must also transmitt and these signals to be recieved by the base. You just wanted a short answer? OK, unlikely you will be able to set up a connection from the North Sea outside Belgium to land over a distance of many km. Most of the radio based antennas are directed towards land where the mobile traffic is. Use VHF or satellite. //J
  10. New sails

    The power of Sailing Anarchy!
  11. Keel joint cracks - epoxy?

    Very true, these words. Where Jack sees close to immediate disaster I just see the same rust we all (in Sweden with the temp diffs) have with steel keels. I have about the same on my boat, and had similar on the previous ... and so has all other with steel keels (in Sweden ...). This Prima is about 15 years old. Far too early for the keel bolts to be in danger - depends of course on where the boat has been, how it has been sailed and so on. If one feels unsure it is possible to check the keel bolts torque as Jack mentions; I did that on a previous boat - torque was beyond the designers values. To drop the keel is a huge operation, not something to embark on without substantial reason. Glassing in the keel blade is to invite problems with rust. Maybe a previous owner wanted to "improve" the blade profile - that was popular some years ago. The flanges are probably glassed in to give a smooth surface. Myself, I would remove all that and paint with epoxy. OTOH - not very critical. The rust seen in the picture should be stopped, however. You do not want this to develop. //J
  12. Keel joint cracks - epoxy?

    No so large, from the picture it looks like it is just some 10 cm wide at each side, measured from the keel blade. Just a good way to spread the loads over a wider area, in contrast to some other boats that have been discussed. There is no information indicating it has been glassed over. Painted, yes of course. //J
  13. Keel joint cracks - epoxy?

    Yes, most likely. The usual theory goes along the difference in thermal expansion of steel and GRP and the difference in temps when on the hard in a climate as in Sweden: difference in thermall expansion coefficient is about a factor of 2 (depends very much on GRP, glass fibre orientation and so on) and temp swing is 50-60 centigrade. Steel alwyas rust, we can just slow down the process. Sooner or later you will get som rust spots on the blade as well - that is just natural. To some extent the rust is merely cosmetic, but it is always good to control it. In particular in the area wher the keel is bonded to the hull rust should be kept to a minimum, ironically that is also the area where rust appears most easily due to the reason mentioned above. Walk around in the "boat yard" where you have your boat, look at the different keels. Most are made in steel, and most have some rust spots. Good luck with the work. //J
  14. Keel joint cracks - epoxy?

    On that I am not so sure. Stell frames use to be either inside - maybe bonded with grp, but still on the inside, as frames. Or on the outside. Again guessing, this is something on the outside, bit wider than usual, to give a large attachment area. That would be a good way to handle to rather high loads from the sail area and bulb hanging ~ 2.5 m down. So I think this is a part of the keel blade. (there could even be a corresponding steel frame on the inside - that would be a very solid construction. OK, this is a guess. I did see what the OP answered, but to have a steel fram in the laminate is unusual. And dumb. But of course, you never know.th If it is as I guess, it is simple to fix. If it is as you (Blitz) say, then .... more difficult. //J
  15. Keel joint cracks - epoxy?

    Most probably the case. I was sloppy earlier on. But there is something in steel attached to the hull, lead doesnt coorode- not in this way at least. Ballast probably as a bulb - maybe there is a steel thing between the bulb and the hull? //J